# Anticipatory Postural Control

**URL:** <http://discourse.iapct.org/t/anticipatory-postural-control/1164>\
**Category:** CSG2019\
**Created:** [May 9, 2019, 1:00am UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164 "2019-05-09T01:00:56Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![rsmarken](http://discourse.iapct.org/user_avatar/discourse.iapct.org/rsmarken/32/3553_2.png) [@rsmarken](http://discourse.iapct.org/u/rsmarken)\
**Post date:** [May 9, 2019, 1:00am UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/1 "2019-05-09T01:00:56Z")

</div>

[Rick Marken 2019-05-08\_17:57:30]

RM: Some time ago Heather Broccard-Bell asked me what the PCT explanation might be of a behavior that looks like a pretty robust example of anticipatory (or feedforward) control. Here’s how Heather described it to me:

> HB-B: I was reading about this finding (and perhaps you are already familiar) that, if if you measure muscle activation during behavior, you often see compensatory activation of the axial musculature well before you get activation in the muscles that direct the part of the body that does the thing you’re focused on. For example, they trained cats to bat at a target with their forepaw. \*\*Well before the limb/forepaw muscles are active, there is activation in the trunk musculature, seemingly anticipating the requisite compensatory stabilization that will become necessary when the forepaw is lifted. \*\* I am wondering what a PCT perspective might be on that? What is the relevant controlled variable, since the thing that actually changes sensory input that should activate control architecture hasn’t yet happened? Am I missing something? It appears to be a rather robust finding.[emphasis mine–RM]

RM: This finding certainly looks like it is inconsistent with the predictions of PCT since it looks like the cat is generating an output (activation of the trunk musculature) open loop in anticipation of a future disturbance (the change in orientation of the body when the forepaw is lifted, a change in orientation that would cause the cat to lose its balance if the trunk were not in the proper position).Â

RM: Apparently, quite a lot of research has been (and is still being) done on this “anticipatory postural control” phenomenon. Here is a paper by Aruin and Latash that Heather sent on the finding of "anticipatory postural control"Â when people drop a weight:

 [https://www.dropbox.com/s/hat2ua3ah7rqs79/aruin1995.pdf?dl=0](https://www.dropbox.com/s/hat2ua3ah7rqs79/aruin1995.pdf?dl=0)

RM: Here there is again clear evidence that the person takes compensatory action (contracts muscles) in anticipation of a future disturbance that would cause a loss of balance if the anticipatory compensation had not occurred.Â

RM: Heather also described this related neurophysiological observation:

> HB-B: \*\*Related, it was discovered that if you knock out the indirect pathway from motor cortex to spinal cord (through the reticular formation), but leave the direct pathway intact, you abolish the “prestabilizing”, but still get the paw bat. \*\* I think you could explain that, in a super-oversimplified way, in terms of those pathways being about different control systems (these bastards have ascending, descending, and reciprocal connections at every level, not to mention all kinds of built-in sensory elements and sensory inputs connecting from elsewhere, as any good ultracomplex biological control system would).

RM: I am posting this to you experts on PCT (with Heather’s permission) because I think this is a very interesting discovery that seems to pose a challenge to PCT and I would like to see what you think about this. I have an idea about how PCT would explain this “anticipatory postural control” phenomenon and I think the  Aruin and Latash paper pointed to above suggests a way to test it. But before I give my PCT explanation I’d like to see what you think.Â

BestÂ

Rick

> **···**
>
> –  
> Richard S. MarkenÂ
> 
> "Perfection is achieved not when you have nothing more to add, but when you  
> have nothing left to take away.�  
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â --Antoine de Saint-Exupery

---

<div class="post-metadata">

**Author:** ![MartinT](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/m/ee7513/32.png) [@MartinT](http://discourse.iapct.org/u/MartinT)\
**Post date:** [May 9, 2019, 4:16am UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/2 "2019-05-09T04:16:09Z")

</div>

[Martin Taylor 2019.05.09.00.09]

> [Rick Marken 2019-05-08\_17:57:30]

> 

> ```
> RM: Some time ago Heather Broccard-Bell asked me what
> 
> ```
> 
> the PCT explanation might be of a behavior that looks like  
> a pretty robust example of anticipatory (or feedforward)  
> control. Here’s how Heather described it to me:

> 

> > ```
> > HB-B: I was reading
> > 
> > ```
> > 
> > about this finding (and perhaps you are already  
> > familiar) that, if if you measure muscle activation  
> > during behavior, you often see compensatory activation  
> > of the axial musculature well before you get activation  
> > in the muscles that direct the part of the body that  
> > does the thing you’re focused on. For example, they  
> > trained cats to bat at a target with their forepaw. \*\* Well  
> > before the limb/forepaw muscles are active, there is  
> > activation in the trunk musculature, seemingly  
> > anticipating the requisite compensatory stabilization  
> > that will become necessary when the forepaw is  
> > lifted. \*\* I am wondering what a PCT perspective  
> > might be on that? What is the relevant controlled  
> > variable, since the thing that actually changes sensory  
> > input that should activate control architecture hasn’t  
> > yet happened? Am I missing something? It appears to be  
> > a rather robust finding.[emphasis mine–RM]

> …

> ```
> RM: I am posting this to you experts on PCT
> 
> ```
> 
> (with Heather’s permission) because I think this is a very  
> interesting discovery that seems to pose a challenge to  
> PCT and I would like to see what you think about this.

```
Here is section of what I wrote to Heather on this question April

```

1. 

> **···**
>
> * * *
> 
> ```
> [Here is a] quick and dirty PCT approach. I start with the intention
> 
> ```
> 
> to bat at the target, which would set a reference for a sequence  
> that could crudely be taken as “store energy, set trigger, wait,  
> release energy when required”, or in a more general sense “Prepare,  
> wait, execute”. You call the storage “prestabilizing”, but I think  
> Powers would have called that a “dormitive principle” that just  
> labels what happens without in any way explaining how or why. The  
> “stabilizing” is postural control of the normal kind, the same as  
> would happen if you pushed the cat. If you have seen a video of the  
> “Big Dog” robot, you have seen this kind of stabilization.
> 
> ```
> The magician Harry Houdini died because he hadn't stored the energy
> 
> ```
> 
> to resist a blow to his abdomen when someone hit him before he was  
> prepared, which he did by tensing (supplying energy to) the stomach  
> muscles. He had offered a general challenge that nobody could hit  
> him there hard enough to hurt him, but the hitter was supposed to do  
> it in a formal kind of way, when he was prepared. When the fatal  
> blow was struck, his muscles had insufficient stored energy to  
> oppose the shock energy in the blow.
> 
> ```
> I think the actual stabilization is simply the use of some of the
> 
> ```
> 
> pre-tensioned stored energy in normal postural control against a  
> force that would be destabilizing, but instead of the control being  
> entirely to oppose a sensed disturbance, it is part of the output  
> side support of the sequence controller. The “bat” is not simply  
> sending reference values to muscles that move the paw relative to  
> the torso, it is sending reference values to all the postural  
> muscles in a temporal pattern that has been reorganized into the  
> control hierarchy in the same way as a trained athlete such as a  
> ballerina coordinates the timings and strengths of her muscle  
> movements so that what an observer calls “the” action doesn’t  
> interfere with her balance.
> 
> ```
> Anyway, those are my first thoughts on the question, before
> 
> ```
> 
> breakfast.
> 
> ```
> -------
> 
> I haven't considered the problem since then, but I thought I might
> 
> ```
> 
> offer the suggestion.
> 
> ```
> The saying "Reculer pour mieux sauter" seems to be about the same
> 
> ```
> 
> phenomenon.
> 
> ```
> Martin
> 
> ```

---

<div class="post-metadata">

**Author:** ![Heather\_Broccard-Bel](http://discourse.iapct.org/user_avatar/discourse.iapct.org/heather_broccard-bel/32/43_2.png) [@Heather\_Broccard-Bel](http://discourse.iapct.org/u/Heather_Broccard-Bel)\
**Post date:** [May 9, 2019, 1:28pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/3 "2019-05-09T13:28:29Z")

</div>

I suspect that the attached (Aruin, 2003) paper goes some way toward reconciling the “invariant, pre-programmed” feedforward conceptualization with the actual phenomenon: namely, it’s not really invariant (or, well, it’s not invariant in that there is a pre-programmed set of muscles activated in a pre-programmed way). So, I suspect that some of the problem in the “mainstream” is semantic.

Anyway, long (~500 ms) stimulation of motor cortex has already demonstrated that “motor output” seems to be about goals, and not specific, muscle-by-muscle motor programs (see Graziano, 2002; attached), and really the only way you could get that to work is hierarchical control with continuous feedback…

[aruin2003.pdf](http://discourse.iapct.org/uploads/short-url/lbIn3twMy6SAnD9oDOvTEyz9Xzb.pdf) (82 KB)

[graziano2002.pdf](http://discourse.iapct.org/uploads/short-url/qZ05gHDV0sisqHrUiH2jZsJYQaV.pdf) (267 KB)

> **···**
>
> On Wed, May 8, 2019, 21:16 Martin Taylor [csgnet@lists.illinois.edu](mailto:csgnet@lists.illinois.edu) wrote:
> 
> > [Martin Taylor 2019.05.09.00.09]
> > 
> > > [Rick Marken 2019-05-08\_17:57:30]
> 
> > >
> 
> > > ```
> > > RM: Some time ago Heather Broccard-Bell asked me what
> > > 
> > > ```
> > > 
> > > the PCT explanation might be of a behavior that looks like  
> > > a pretty robust example of anticipatory (or feedforward)  
> > > control. Here’s how Heather described it to me:
> 
> > >
> 
> > > > ```
> > > > HB-B: I was reading
> > > > 
> > > > ```
> > > > 
> > > > about this finding (and perhaps you are already  
> > > > familiar) that, if if you measure muscle activation  
> > > > during behavior, you often see compensatory activation  
> > > > of the axial musculature well before you get activation  
> > > > in the muscles that direct the part of the body that  
> > > > does the thing you’re focused on. For example, they  
> > > > trained cats to bat at a target with their forepaw. \*\* Well  
> > > > before the limb/forepaw muscles are active, there is  
> > > > activation in the trunk musculature, seemingly  
> > > > anticipating the requisite compensatory stabilization  
> > > > that will become necessary when the forepaw is  
> > > > lifted. \*\* I am wondering what a PCT perspective  
> > > > might be on that? What is the relevant controlled  
> > > > variable, since the thing that actually changes sensory  
> > > > input that should activate control architecture hasn’t  
> > > > yet happened? Am I missing something? It appears to be  
> > > > a rather robust finding.[emphasis mine–RM]
> 
> > > …
> 
> > > ```
> > > RM: I am posting this to you experts on PCT
> > > 
> > > ```
> > > 
> > > (with Heather’s permission) because I think this is a very  
> > > interesting discovery that seems to pose a challenge to  
> > > PCT and I would like to see what you think about this.
> 
> > ```
> > Here is section of what I wrote to Heather on this question April
> > 
> > ```
> > 
> > 1. 
> > 
> > ```
> > --------
> > 
> > [Here is a] quick and dirty PCT approach. I start with the intention
> > 
> > ```
> > 
> > to bat at the target, which would set a reference for a sequence  
> > that could crudely be taken as “store energy, set trigger, wait,  
> > release energy when required”, or in a more general sense “Prepare,  
> > wait, execute”. You call the storage “prestabilizing”, but I think  
> > Powers would have called that a “dormitive principle” that just  
> > labels what happens without in any way explaining how or why. The  
> > “stabilizing” is postural control of the normal kind, the same as  
> > would happen if you pushed the cat. If you have seen a video of the  
> > “Big Dog” robot, you have seen this kind of stabilization.
> > 
> > ```
> > The magician Harry Houdini died because he hadn't stored the energy
> > 
> > ```
> > 
> > to resist a blow to his abdomen when someone hit him before he was  
> > prepared, which he did by tensing (supplying energy to) the stomach  
> > muscles. He had offered a general challenge that nobody could hit  
> > him there hard enough to hurt him, but the hitter was supposed to do  
> > it in a formal kind of way, when he was prepared. When the fatal  
> > blow was struck, his muscles had insufficient stored energy to  
> > oppose the shock energy in the blow.
> > 
> > ```
> > I think the actual stabilization is simply the use of some of the
> > 
> > ```
> > 
> > pre-tensioned stored energy in normal postural control against a  
> > force that would be destabilizing, but instead of the control being  
> > entirely to oppose a sensed disturbance, it is part of the output  
> > side support of the sequence controller. The “bat” is not simply  
> > sending reference values to muscles that move the paw relative to  
> > the torso, it is sending reference values to all the postural  
> > muscles in a temporal pattern that has been reorganized into the  
> > control hierarchy in the same way as a trained athlete such as a  
> > ballerina coordinates the timings and strengths of her muscle  
> > movements so that what an observer calls “the” action doesn’t  
> > interfere with her balance.
> > 
> > ```
> > Anyway, those are my first thoughts on the question, before
> > 
> > ```
> > 
> > breakfast.
> > 
> > ```
> > -------
> > 
> > I haven't considered the problem since then, but I thought I might
> > 
> > ```
> > 
> > offer the suggestion.
> > 
> > ```
> > The saying "Reculer pour mieux sauter" seems to be about the same
> > 
> > ```
> > 
> > phenomenon.
> > 
> > ```
> > Martin
> > 
> > ```

---

<div class="post-metadata">

**Author:** ![wmansell](http://discourse.iapct.org/user_avatar/discourse.iapct.org/wmansell/32/36_2.png) [@wmansell](http://discourse.iapct.org/u/wmansell)\
**Post date:** [May 9, 2019, 2:18pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/4 "2019-05-09T14:18:02Z")

</div>

Hurray, PCT wins! But do any of the readers of these papers realise?

> **···**
>
> On 9 May 2019, at 14:28, Heather Broccard-Bell (hebell@ucsd.edu via csgnet Mailing List) [csgnet@lists.illinois.edu](mailto:csgnet@lists.illinois.edu) wrote:
> 
> > 
> 
> > I suspect that the attached (Aruin, 2003) paper goes some way toward reconciling the “invariant, pre-programmed” feedforward conceptualization with the actual phenomenon: namely, it’s not really invariant (or, well, it’s not invariant in that there is a pre-programmed set of muscles activated in a pre-programmed way). So, I suspect that some of the problem in the “mainstream” is semantic.
> 
> > Anyway, long (~500 ms) stimulation of motor cortex has already demonstrated that “motor output” seems to be about goals, and not specific, muscle-by-muscle motor programs (see Graziano, 2002; attached), and really the only way you could get that to work is hierarchical control with continuous feedback…
> 
> > On Wed, May 8, 2019, 21:16 Martin Taylor [csgnet@lists.illinois.edu](mailto:csgnet@lists.illinois.edu) wrote:
> 
> > > [Martin Taylor 2019.05.09.00.09]
> > > 
> > > > [Rick Marken 2019-05-08\_17:57:30]
> 
> > > >
> 
> > > > ```
> > > > RM: Some time ago Heather Broccard-Bell asked me what
> > > > 
> > > > ```
> > > > 
> > > > the PCT explanation might be of a behavior that looks like  
> > > > a pretty robust example of anticipatory (or feedforward)  
> > > > control. Here’s how Heather described it to me:
> 
> > > >
> 
> > > > > ```
> > > > > HB-B: I was reading
> > > > > 
> > > > > ```
> > > > > 
> > > > > about this finding (and perhaps you are already  
> > > > > familiar) that, if if you measure muscle activation  
> > > > > during behavior, you often see compensatory activation  
> > > > > of the axial musculature well before you get activation  
> > > > > in the muscles that direct the part of the body that  
> > > > > does the thing you’re focused on. For example, they  
> > > > > trained cats to bat at a target with their forepaw. \*\* Well  
> > > > > before the limb/forepaw muscles are active, there is  
> > > > > activation in the trunk musculature, seemingly  
> > > > > anticipating the requisite compensatory stabilization  
> > > > > that will become necessary when the forepaw is  
> > > > > lifted. \*\* I am wondering what a PCT perspective  
> > > > > might be on that? What is the relevant controlled  
> > > > > variable, since the thing that actually changes sensory  
> > > > > input that should activate control architecture hasn’t  
> > > > > yet happened? Am I missing something? It appears to be  
> > > > > a rather robust finding.[emphasis mine–RM]
> 
> > > > …
> 
> > > > ```
> > > > RM: I am posting this to you experts on PCT
> > > > 
> > > > ```
> > > > 
> > > > (with Heather’s permission) because I think this is a very  
> > > > interesting discovery that seems to pose a challenge to  
> > > > PCT and I would like to see what you think about this.
> 
> > > ```
> > > Here is section of what I wrote to Heather on this question April
> > > 
> > > ```
> > > 
> > > 1. 
> > > 
> > > ```
> > > --------
> > > 
> > > [Here is a] quick and dirty PCT approach. I start with the intention
> > > 
> > > ```
> > > 
> > > to bat at the target, which would set a reference for a sequence  
> > > that could crudely be taken as “store energy, set trigger, wait,  
> > > release energy when required”, or in a more general sense “Prepare,  
> > > wait, execute”. You call the storage “prestabilizing”, but I think  
> > > Powers would have called that a “dormitive principle” that just  
> > > labels what happens without in any way explaining how or why. The  
> > > “stabilizing” is postural control of the normal kind, the same as  
> > > would happen if you pushed the cat. If you have seen a video of the  
> > > “Big Dog” robot, you have seen this kind of stabilization.
> > > 
> > > ```
> > > The magician Harry Houdini died because he hadn't stored the energy
> > > 
> > > ```
> > > 
> > > to resist a blow to his abdomen when someone hit him before he was  
> > > prepared, which he did by tensing (supplying energy to) the stomach  
> > > muscles. He had offered a general challenge that nobody could hit  
> > > him there hard enough to hurt him, but the hitter was supposed to do  
> > > it in a formal kind of way, when he was prepared. When the fatal  
> > > blow was struck, his muscles had insufficient stored energy to  
> > > oppose the shock energy in the blow.
> > > 
> > > ```
> > > I think the actual stabilization is simply the use of some of the
> > > 
> > > ```
> > > 
> > > pre-tensioned stored energy in normal postural control against a  
> > > force that would be destabilizing, but instead of the control being  
> > > entirely to oppose a sensed disturbance, it is part of the output  
> > > side support of the sequence controller. The “bat” is not simply  
> > > sending reference values to muscles that move the paw relative to  
> > > the torso, it is sending reference values to all the postural  
> > > muscles in a temporal pattern that has been reorganized into the  
> > > control hierarchy in the same way as a trained athlete such as a  
> > > ballerina coordinates the timings and strengths of her muscle  
> > > movements so that what an observer calls “the” action doesn’t  
> > > interfere with her balance.
> > > 
> > > ```
> > > Anyway, those are my first thoughts on the question, before
> > > 
> > > ```
> > > 
> > > breakfast.
> > > 
> > > ```
> > > -------
> > > 
> > > I haven't considered the problem since then, but I thought I might
> > > 
> > > ```
> > > 
> > > offer the suggestion.
> > > 
> > > ```
> > > The saying "Reculer pour mieux sauter" seems to be about the same
> > > 
> > > ```
> > > 
> > > phenomenon.
> > > 
> > > ```
> > > Martin
> > > 
> > > ```
> 
> > \<aruin2003.pdf\>
> 
> > \<graziano2002.pdf\>

---

<div class="post-metadata">

**Author:** ![bleach](http://discourse.iapct.org/user_avatar/discourse.iapct.org/bleach/32/51_2.png) [@bleach](http://discourse.iapct.org/u/bleach)\
**Post date:** [May 9, 2019, 5:50pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/5 "2019-05-09T17:50:53Z")

</div>

May be my conception of PCT in this regard is flawed but I don’t  
see where this is a challenge at all given:

- The arrival of a ball (or other object) to bat is expected

- Or it is planned to drop the weight.  
Then based upon a world view developed through experience, the  
mental system has a model that shows that preparation results in a  
better overall outcome:

- 

```
    There is a reference for maintaining a specific spatial

```

orientation (batting at something to avoid attack by another  
purposeful being for example)

- 

```
    There is a reference for not falling over (or having to

```

stumble to maintain balance).  
Now if such pre-action tensioning occurs without any anticipation  
for the need, then yes I have a problem.

-bill

> **···**
>
> On 5/8/19 7:00 PM, Richard Marken  
> ( via csgnet Mailing List) wrote:
> 
> [rsmarken@gmail.com](mailto:rsmarken@gmail.com)
> 
> > [Rick Marken 2019-05-08\_17:57:30]
> 
> > 
> 
> > ```
> > RM: Some time ago Heather Broccard-Bell asked me what
> > 
> > ```
> > 
> > the PCT explanation might be of a behavior that looks like  
> > a pretty robust example of anticipatory (or feedforward)  
> > control. Here’s how Heather described it to me:
> 
> > 
> 
> > > ```
> > > HB-B: I was reading
> > > 
> > > ```
> > > 
> > > about this finding (and perhaps you are already  
> > > familiar) that, if if you measure muscle activation  
> > > during behavior, you often see compensatory activation  
> > > of the axial musculature well before you get activation  
> > > in the muscles that direct the part of the body that  
> > > does the thing you’re focused on. For example, they  
> > > trained cats to bat at a target with their forepaw. \*\* Well  
> > > before the limb/forepaw muscles are active, there is  
> > > activation in the trunk musculature, seemingly  
> > > anticipating the requisite compensatory stabilization  
> > > that will become necessary when the forepaw is  
> > > lifted. \*\* I am wondering what a PCT perspective  
> > > might be on that? What is the relevant controlled  
> > > variable, since the thing that actually changes sensory  
> > > input that should activate control architecture hasn’t  
> > > yet happened? Am I missing something? It appears to be  
> > > a rather robust finding.[emphasis mine–RM]
> 
> > ```
> > RM: This finding certainly looks like it is
> > 
> > ```
> > 
> > inconsistent with the predictions of PCT since it looks  
> > like the cat is generating an output (activation of the  
> > trunk musculature) open loop in anticipation of a future  
> > disturbance (the change in orientation of the body when  
> > the forepaw is lifted, a change in orientation that  
> > would cause the cat to lose its balance if the trunk  
> > were not in the proper position).Â
> 
> > 
> 
> > ```
> > RM: Apparently, quite a lot of research has been (and
> > 
> > ```
> > 
> > is still being) done on this “anticipatory postural  
> > control” phenomenon. Here is a paper by Aruin and  
> > Latash that Heather sent on the finding of "anticipatory  
> > postural control"Â when people drop a weight:
> 
> > 
> 
> > Â [https://www.dropbox.com/s/hat2ua3ah7rqs79/aruin1995.pdf?dl=0](https://urldefense.proofpoint.com/v2/url?u=https-3A__www.dropbox.com_s_hat2ua3ah7rqs79_aruin1995.pdf-3Fdl-3D0&d=DwMDaQ&c=OCIEmEwdEq_aNlsP4fF3gFqSN-E3mlr2t9JcDdfOZag&r=G2rjwc9SjlT6Blyc8su_Md8P_xOsOTRMJ5teQVBC2qU&m=zknzuh242fhviPJl4TwTfTf6XtRye1r4GPLCfBEUUTg&s=3dWq9bosChkJc_XmOClF7t86gVhS6PiwFxxurUW-2Oc&e=)
> 
> > 
> 
> > ```
> > RM: Here there is again clear evidence that the
> > 
> > ```
> > 
> > person takes compensatory action (contracts muscles) in  
> > anticipation of a future disturbance that would cause a  
> > loss of balance if the anticipatory compensation had not  
> > occurred.Â
> 
> > 
> 
> > ```
> > RM: Heather also described this related
> > 
> > ```
> > 
> > neurophysiological observation:
> 
> > 
> 
> > > HB-B: \*\* Related, it  
> > > was discovered that if you knock out the indirect  
> > > pathway from motor cortex to spinal cord (through the  
> > > reticular formation), but leave the direct pathway  
> > > intact, you abolish the “prestabilizing”, but still  
> > > get the paw bat. \*\* I think you could explain that,  
> > > in a super-oversimplified way, in terms of those  
> > > pathways being about different control systems (these  
> > > bastards have ascending, descending, and reciprocal  
> > > connections at every level, not to mention all kinds of  
> > > built-in sensory elements and sensory inputs connecting  
> > > from elsewhere, as any good ultracomplex biological  
> > > control system would).
> 
> > ```
> > RM: I am posting this to you experts on PCT
> > 
> > ```
> > 
> > (with Heather’s permission) because I think this is a very  
> > interesting discovery that seems to pose a challenge to  
> > PCT and I would like to see what you think about this. I  
> > have an idea about how PCT would explain this  
> > “anticipatory postural control” phenomenon and I think  
> > the  Aruin and Latash paper pointed to above suggests a  
> > way to test it. But before I give my PCT explanation I’d  
> > like to see what you think.Â
> 
> > 
> 
> > BestÂ
> 
> > 
> 
> > Rick
> 
> > 
> 
> > –  
> > Richard S. MarkenÂ
> 
> > ```
> > "Perfection
> > 
> > ```
> > 
> > is achieved not when you have  
> > nothing more to add, but when  
> > you  
> > have  
> > nothing left to take away.�  
> > Â  
> > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  
> > –Antoine de Saint-Exupery

---

<div class="post-metadata">

**Author:** ![Heather\_Broccard-Bel](http://discourse.iapct.org/user_avatar/discourse.iapct.org/heather_broccard-bel/32/43_2.png) [@Heather\_Broccard-Bel](http://discourse.iapct.org/u/Heather_Broccard-Bel)\
**Post date:** [May 9, 2019, 5:53pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/6 "2019-05-09T17:53:48Z")

</div>

I’m still not sure I satisfactorily answered my own original question, though. And also, if we can compensate for a predicted disturbance (even if we can update our compensation when the compensation is perturbed), the original reference signal is presumably coming from some kind of internal model, no? Is this cool? I thought we were anti-internal model (except for super sophisticated human cognition where we do clearly imagine things)? This suggests cats have one, no?

> **···**
>
> On Thu, May 9, 2019, 07:18 Warren Mansell [wmansell@gmail.com](mailto:wmansell@gmail.com) wrote:
> 
> > Hurray, PCT wins! But do any of the readers of these papers realise?
> 
> > 
> 
> > On 9 May 2019, at 14:28, Heather Broccard-Bell (hebell@ucsd.edu via csgnet Mailing List) [csgnet@lists.illinois.edu](mailto:csgnet@lists.illinois.edu) wrote:
> 
> > >
> 
> > > I suspect that the attached (Aruin, 2003) paper goes some way toward reconciling the “invariant, pre-programmed” feedforward conceptualization with the actual phenomenon: namely, it’s not really invariant (or, well, it’s not invariant in that there is a pre-programmed set of muscles activated in a pre-programmed way). So, I suspect that some of the problem in the “mainstream” is semantic.
> 
> > > Anyway, long (~500 ms) stimulation of motor cortex has already demonstrated that “motor output” seems to be about goals, and not specific, muscle-by-muscle motor programs (see Graziano, 2002; attached), and really the only way you could get that to work is hierarchical control with continuous feedback…
> 
> > > On Wed, May 8, 2019, 21:16 Martin Taylor [csgnet@lists.illinois.edu](mailto:csgnet@lists.illinois.edu) wrote:
> 
> > > > [Martin Taylor 2019.05.09.00.09]
> > > > 
> > > > > [Rick Marken 2019-05-08\_17:57:30]
> 
> > > > >
> 
> > > > > ```
> > > > > RM: Some time ago Heather Broccard-Bell asked me what
> > > > > 
> > > > > ```
> > > > > 
> > > > > the PCT explanation might be of a behavior that looks like  
> > > > > a pretty robust example of anticipatory (or feedforward)  
> > > > > control. Here’s how Heather described it to me:
> 
> > > > >
> 
> > > > > > ```
> > > > > > HB-B: I was reading
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > about this finding (and perhaps you are already  
> > > > > > familiar) that, if if you measure muscle activation  
> > > > > > during behavior, you often see compensatory activation  
> > > > > > of the axial musculature well before you get activation  
> > > > > > in the muscles that direct the part of the body that  
> > > > > > does the thing you’re focused on. For example, they  
> > > > > > trained cats to bat at a target with their forepaw. \*\* Well  
> > > > > > before the limb/forepaw muscles are active, there is  
> > > > > > activation in the trunk musculature, seemingly  
> > > > > > anticipating the requisite compensatory stabilization  
> > > > > > that will become necessary when the forepaw is  
> > > > > > lifted. \*\* I am wondering what a PCT perspective  
> > > > > > might be on that? What is the relevant controlled  
> > > > > > variable, since the thing that actually changes sensory  
> > > > > > input that should activate control architecture hasn’t  
> > > > > > yet happened? Am I missing something? It appears to be  
> > > > > > a rather robust finding.[emphasis mine–RM]
> 
> > > > > …
> 
> > > > > ```
> > > > > RM: I am posting this to you experts on PCT
> > > > > 
> > > > > ```
> > > > > 
> > > > > (with Heather’s permission) because I think this is a very  
> > > > > interesting discovery that seems to pose a challenge to  
> > > > > PCT and I would like to see what you think about this.
> 
> > > > ```
> > > > Here is section of what I wrote to Heather on this question April
> > > > 
> > > > ```
> > > > 
> > > > 1. 
> > > > 
> > > > ```
> > > > --------
> > > > 
> > > > [Here is a] quick and dirty PCT approach. I start with the intention
> > > > 
> > > > ```
> > > > 
> > > > to bat at the target, which would set a reference for a sequence  
> > > > that could crudely be taken as “store energy, set trigger, wait,  
> > > > release energy when required”, or in a more general sense “Prepare,  
> > > > wait, execute”. You call the storage “prestabilizing”, but I think  
> > > > Powers would have called that a “dormitive principle” that just  
> > > > labels what happens without in any way explaining how or why. The  
> > > > “stabilizing” is postural control of the normal kind, the same as  
> > > > would happen if you pushed the cat. If you have seen a video of the  
> > > > “Big Dog” robot, you have seen this kind of stabilization.
> > > > 
> > > > ```
> > > > The magician Harry Houdini died because he hadn't stored the energy
> > > > 
> > > > ```
> > > > 
> > > > to resist a blow to his abdomen when someone hit him before he was  
> > > > prepared, which he did by tensing (supplying energy to) the stomach  
> > > > muscles. He had offered a general challenge that nobody could hit  
> > > > him there hard enough to hurt him, but the hitter was supposed to do  
> > > > it in a formal kind of way, when he was prepared. When the fatal  
> > > > blow was struck, his muscles had insufficient stored energy to  
> > > > oppose the shock energy in the blow.
> > > > 
> > > > ```
> > > > I think the actual stabilization is simply the use of some of the
> > > > 
> > > > ```
> > > > 
> > > > pre-tensioned stored energy in normal postural control against a  
> > > > force that would be destabilizing, but instead of the control being  
> > > > entirely to oppose a sensed disturbance, it is part of the output  
> > > > side support of the sequence controller. The “bat” is not simply  
> > > > sending reference values to muscles that move the paw relative to  
> > > > the torso, it is sending reference values to all the postural  
> > > > muscles in a temporal pattern that has been reorganized into the  
> > > > control hierarchy in the same way as a trained athlete such as a  
> > > > ballerina coordinates the timings and strengths of her muscle  
> > > > movements so that what an observer calls “the” action doesn’t  
> > > > interfere with her balance.
> > > > 
> > > > ```
> > > > Anyway, those are my first thoughts on the question, before
> > > > 
> > > > ```
> > > > 
> > > > breakfast.
> > > > 
> > > > ```
> > > > -------
> > > > 
> > > > I haven't considered the problem since then, but I thought I might
> > > > 
> > > > ```
> > > > 
> > > > offer the suggestion.
> > > > 
> > > > ```
> > > > The saying "Reculer pour mieux sauter" seems to be about the same
> > > > 
> > > > ```
> > > > 
> > > > phenomenon.
> > > > 
> > > > ```
> > > > Martin
> > > > 
> > > > ```
> 
> > > \<aruin2003.pdf\>
> 
> > > \<graziano2002.pdf\>

---

<div class="post-metadata">

**Author:** ![Heather\_Broccard-Bel](http://discourse.iapct.org/user_avatar/discourse.iapct.org/heather_broccard-bel/32/43_2.png) [@Heather\_Broccard-Bel](http://discourse.iapct.org/u/Heather_Broccard-Bel)\
**Post date:** [May 9, 2019, 7:17pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/7 "2019-05-09T19:17:57Z")

</div>

I see that according to Bill Leach, internal models are allowed. So then the question becomes, does the PCT interpretation generate any predictions that are meaningfully different from the “mainstream” approaches would predict?

> **···**
>
> Heather C. Broccard-Bell, Ph.D.
> 
> Adjunct Assistant Professor
> 
> Department of Psychological Sciences
> 
> University of San Diego
> 
> Visiting Scholar
> 
> The role of noise / variability in complex, adaptive systems
> 
> Nieh Honey Bee Lab
> 
> Division of Biological Sciences; Section of Ecology, Behavior, and Evolution
> 
> University of California San Diego
> 
> 619.757.4694

---

<div class="post-metadata">

**Author:** ![bleach](http://discourse.iapct.org/user_avatar/discourse.iapct.org/bleach/32/51_2.png) [@bleach](http://discourse.iapct.org/u/bleach)\
**Post date:** [May 9, 2019, 7:53pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/8 "2019-05-09T19:53:43Z")

</div>

Heather,

```
  I don't know if it was Rick or Martin or both that mentioned

```

sequence level. Preparing muscles for an action that is perceived  
to be soon required is not beyond the realm of PCT.

```
  No, I don't think you can claim that models are outside of PCT

```

concepts. It is easily argued (in my opinion) that even some of  
the physical neural structures themselves are indeed model based.  
That is they are arranged and ‘rewired’ by the reorganizing system  
(or inherited from an ancestral reorganization) to function  
optimally.

```
  The postulated program level is implicitly model based (as are

```

all programs, computer or otherwise).

```
  I missed your original post so I am quite delighted that Rick

```

mentioned it and that has had the result of renewing discussion of  
the idea.

bill

> **···**
>
> On 5/9/19 11:53 AM, Heather  
> Broccard-Bell ( via csgnet Mailing List) wrote:
> 
> hebell@ucsd.edu
> 
> > ```
> > I'm still not sure I satisfactorily answered my
> > 
> > ```
> > 
> > own original question, though. And also, if we can compensate  
> > for a predicted disturbance (even if we can update our  
> > compensation when the compensation is perturbed), the original  
> > reference signal is presumably coming from some kind of internal  
> > model, no? Is this cool? I thought we were anti-internal model  
> > (except for super sophisticated human cognition where we do  
> > clearly imagine things)? This suggests cats have one, no?
> 
> > ```
> > On Thu, May 9, 2019, 07:18
> > 
> > ```
> > 
> > Warren Mansell \<[wmansell@gmail.com](mailto:wmansell@gmail.com) \>  
> > wrote:
> 
> > > ```
> > > Hurray, PCT wins! But do any of the
> > > 
> > > ```
> > > 
> > > readers of these papers realise?
> 
> > >
> 
> > > ```
> > > On 9 May 2019, at 14:28, Heather Broccard-Bell (hebell@ucsd.edu
> > > via csgnet Mailing List) <csgnet@lists.illinois.edu >
> > > 
> > > ```
> > > 
> > > wrote:
> 
> > > >
> 
> > > > ```
> > > > I suspect that the attached
> > > > 
> > > > ```
> > > > 
> > > > (Aruin, 2003) paper goes some way toward  
> > > > reconciling the “invariant, pre-programmed”  
> > > > feedforward conceptualization with the  
> > > > actual phenomenon: namely, it’s not really  
> > > > invariant (or, well, it’s not invariant in  
> > > > that there is a pre-programmed set of  
> > > > muscles activated in a pre-programmed way).  
> > > > So, I suspect that some of the problem in  
> > > > the “mainstream” is semantic.
> 
> > > > ```
> > > > Anyway, long (~500 ms)
> > > > 
> > > > ```
> > > > 
> > > > stimulation of motor cortex has already  
> > > > demonstrated that “motor output” seems to  
> > > > be about goals, and not specific,  
> > > > muscle-by-muscle motor programs (see  
> > > > Graziano, 2002; attached), and really the  
> > > > only way you could get that to work is  
> > > > hierarchical control with continuous  
> > > > feedback…
> 
> > > > ```
> > > > On Wed,
> > > > 
> > > > ```
> > > > 
> > > > May 8, 2019, 21:16 Martin Taylor \<csgnet@lists.illinois.edu \>  
> > > > wrote:
> 
> > > > > [Martin Taylor 2019.05.09.00.09]
> > > > > 
> > > > > > ```
> > > > > > [Rick Marken
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > 2019-05-08\_17:57:30]
> 
> > > > > >
> 
> > > > > > ```
> > > > > > RM: Some time ago Heather
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > Broccard-Bell asked me what  
> > > > > > the PCT explanation might be  
> > > > > > of a behavior that looks like  
> > > > > > a pretty robust example of  
> > > > > > anticipatory (or feedforward)  
> > > > > > control. Here’s how Heather  
> > > > > > described it to me:
> 
> > > > > >
> 
> > > > > > > ```
> > > > > > > HB-B: I was reading about this
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > finding (and perhaps you are  
> > > > > > > already familiar) that, if  
> > > > > > > if you measure muscle  
> > > > > > > activation during behavior,  
> > > > > > > you often see compensatory  
> > > > > > > activation of the axial  
> > > > > > > musculature well before you  
> > > > > > > get activation in the  
> > > > > > > muscles that direct the part  
> > > > > > > of the body that does the  
> > > > > > > thing you’re focused on.  
> > > > > > > For example, they trained  
> > > > > > > cats to bat at a target with  
> > > > > > > their forepaw. \*\* Well  
> > > > > > > before the limb/forepaw  
> > > > > > > muscles are active, there  
> > > > > > > is activation in the trunk  
> > > > > > > musculature, seemingly  
> > > > > > > anticipating the requisite  
> > > > > > > compensatory stabilization  
> > > > > > > that will become necessary  
> > > > > > > when the forepaw is  
> > > > > > > lifted. \*\* I am  
> > > > > > > wondering what a PCT  
> > > > > > > perspective might be on  
> > > > > > > that? What is the relevant  
> > > > > > > controlled variable, since  
> > > > > > > the thing that actually  
> > > > > > > changes sensory input that  
> > > > > > > should activate control  
> > > > > > > architecture hasn’t yet  
> > > > > > > happened? Am I missing  
> > > > > > > something? It appears to be  
> > > > > > > a rather robust  
> > > > > > > finding.[emphasis mine–RM]
> 
> > > > > > …
> 
> > > > > > ```
> > > > > > RM: I am posting
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > this to you experts on PCT  
> > > > > > (with Heather’s permission)  
> > > > > > because I think this is a very  
> > > > > > interesting discovery that  
> > > > > > seems to pose a challenge to  
> > > > > > PCT and I would like to see  
> > > > > > what you think about this.
> 
> > > > > ```
> > > > > Here is section of what I wrote to
> > > > > 
> > > > > ```
> > > > > 
> > > > > Heather on this question April 12.
> > > > > 
> > > > > ```
> > > > > --------
> > > > > 
> > > > > [Here is a] quick and dirty PCT
> > > > > 
> > > > > ```
> > > > > 
> > > > > approach. I start with the intention to  
> > > > > bat at the target, which would set a  
> > > > > reference for a sequence that could  
> > > > > crudely be taken as “store energy, set  
> > > > > trigger, wait, release energy when  
> > > > > required”, or in a more general sense  
> > > > > “Prepare, wait, execute”. You call the  
> > > > > storage “prestabilizing”, but I think  
> > > > > Powers would have called that a  
> > > > > “dormitive principle” that just labels  
> > > > > what happens without in any way  
> > > > > explaining how or why. The “stabilizing”  
> > > > > is postural control of the normal kind,  
> > > > > the same as would happen if you pushed  
> > > > > the cat. If you have seen a video of the  
> > > > > “Big Dog” robot, you have seen this kind  
> > > > > of stabilization.
> > > > > 
> > > > > ```
> > > > > The magician Harry Houdini died because
> > > > > 
> > > > > ```
> > > > > 
> > > > > he hadn’t stored the energy to resist a  
> > > > > blow to his abdomen when someone hit him  
> > > > > before he was prepared, which he did by  
> > > > > tensing (supplying energy to) the  
> > > > > stomach muscles. He had offered a  
> > > > > general challenge that nobody could hit  
> > > > > him there hard enough to hurt him, but  
> > > > > the hitter was supposed to do it in a  
> > > > > formal kind of way, when he was  
> > > > > prepared. When the fatal blow was  
> > > > > struck, his muscles had insufficient  
> > > > > stored energy to oppose the shock energy  
> > > > > in the blow.
> > > > > 
> > > > > ```
> > > > > I think the actual stabilization is
> > > > > 
> > > > > ```
> > > > > 
> > > > > simply the use of some of the  
> > > > > pre-tensioned stored energy in normal  
> > > > > postural control against a force that  
> > > > > would be destabilizing, but instead of  
> > > > > the control being entirely to oppose a  
> > > > > sensed disturbance, it is part of the  
> > > > > output side support of the sequence  
> > > > > controller. The “bat” is not simply  
> > > > > sending reference values to muscles that  
> > > > > move the paw relative to the torso, it  
> > > > > is sending reference values to all the  
> > > > > postural muscles in a temporal pattern  
> > > > > that has been reorganized into the  
> > > > > control hierarchy in the same way as a  
> > > > > trained athlete such as a ballerina  
> > > > > coordinates the timings and strengths of  
> > > > > her muscle movements so that what an  
> > > > > observer calls “the” action doesn’t  
> > > > > interfere with her balance.
> > > > > 
> > > > > ```
> > > > > Anyway, those are my first thoughts on
> > > > > 
> > > > > ```
> > > > > 
> > > > > the question, before breakfast.
> > > > > 
> > > > > ```
> > > > > -------
> > > > > 
> > > > > I haven't considered the problem since
> > > > > 
> > > > > ```
> > > > > 
> > > > > then, but I thought I might offer the  
> > > > > suggestion.
> > > > > 
> > > > > ```
> > > > > The saying "Reculer pour mieux sauter"
> > > > > 
> > > > > ```
> > > > > 
> > > > > seems to be about the same phenomenon.
> > > > > 
> > > > > ```
> > > > > Martin
> > > > > 
> > > > > ```
> 
> > > > \<aruin2003.pdf\>
> 
> > > > \<graziano2002.pdf\>

---

<div class="post-metadata">

**Author:** ![\_Erling\_Jorgensen](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/_/58956e/32.png) [@\_Erling\_Jorgensen](http://discourse.iapct.org/u/_Erling_Jorgensen)\
**Post date:** [May 9, 2019, 7:54pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/9 "2019-05-09T19:54:00Z")

</div>

[From Erling Jorgensen (2019.05.09 1530 EDT)]

EJ: To say “internal models” still requires some notion of mechanism, so until that is specified a little better, in my mind the term remains ‘hand waving’. It seems like “pre-action tensioning” is a valid shorthand description of the phenomenon, for which “anticipatory stabilization” had been proposed as an explanation.

EJ: I rather like Martin’s proposal for controlling a prior stage in a sequence. I think of the similarity to how Segway machines are operated, as an analogue for human walking. Before an actual step is taken, there is leaning forward and the center of gravity shifts. I wonder whether that is akin to the “activation in the trunk musculature” that is measured before a cat’s forepaw is actually lifted. But “tensioning a muscle” is still a present moment control process, via equal increase of force to both sides of an opponent-process muscle. It requires neither anticipatory effects nor discernible movement.

EJ: I appreciate the way Heather is fashioning the question, in terms of “meaningfully different predictions”. The standard PCT model says output is generated by error already occurring, which means either a disturbance moved an existing perception away from its preferred value, or a change in reference happened toward which the perception now moves. Feedforward effects are a different model, and it is not yet clear whether PCT has yet had to make much use of such mechanisms.

Erling

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> > > “Heather Broccard-Bell” (hebell@ucsd.edu via csgnet Mailing List) [csgnet@lists.illinois.edu](mailto:csgnet@lists.illinois.edu) 5/9/2019 3:17 PM \>\>\>

- **CAUTION** - This is an EXTERNAL email - DO NOT open attachments or links in unexpected emails or from unknown senders \*

I see that according to Bill Leach, internal models are allowed. So then the question becomes, does the PCT interpretation generate any predictions that are meaningfully different from the “mainstream” approaches would predict?

> **···**
>
> Heather C. Broccard-Bell, Ph.D.
> 
> Adjunct Assistant Professor
> 
> Department of Psychological Sciences
> 
> University of San Diego
> 
> Visiting Scholar
> 
> The role of noise / variability in complex, adaptive systems
> 
> Nieh Honey Bee Lab
> 
> Division of Biological Sciences; Section of Ecology, Behavior, and Evolution
> 
> University of California San Diego
> 
> 619.757.4694

---

<div class="post-metadata">

**Author:** ![Heather\_Broccard-Bel](http://discourse.iapct.org/user_avatar/discourse.iapct.org/heather_broccard-bel/32/43_2.png) [@Heather\_Broccard-Bel](http://discourse.iapct.org/u/Heather_Broccard-Bel)\
**Post date:** [May 9, 2019, 7:59pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/10 "2019-05-09T19:59:35Z")

</div>

Sorry, that was meant to go to everyone, not just Martin 🙂

> **···**
>
> Heather C. Broccard-Bell, Ph.D.
> 
> Adjunct Assistant Professor
> 
> Department of Psychological Sciences
> 
> University of San Diego
> 
> Visiting Scholar
> 
> The role of noise / variability in complex, adaptive systems
> 
> Nieh Honey Bee Lab
> 
> Division of Biological Sciences; Section of Ecology, Behavior, and Evolution
> 
> University of California San Diego
> 
> 619.757.4694

---

<div class="post-metadata">

**Author:** ![Heather\_Broccard-Bel](http://discourse.iapct.org/user_avatar/discourse.iapct.org/heather_broccard-bel/32/43_2.png) [@Heather\_Broccard-Bel](http://discourse.iapct.org/u/Heather_Broccard-Bel)\
**Post date:** [May 9, 2019, 8:26pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/11 "2019-05-09T20:26:52Z")

</div>

Also, I totally agree that things like connection changes are some kind of internal model… but was under the (I guess false?) impression that internal representation was not allowed? Just like how signal transduction from sensory receptors is some kind of internal representation…

> **···**
>
> Heather C. Broccard-Bell, Ph.D.
> 
> Adjunct Assistant Professor
> 
> Department of Psychological Sciences
> 
> University of San Diego
> 
> Visiting Scholar
> 
> The role of noise / variability in complex, adaptive systems
> 
> Nieh Honey Bee Lab
> 
> Division of Biological Sciences; Section of Ecology, Behavior, and Evolution
> 
> University of California San Diego
> 
> 619.757.4694

---

<div class="post-metadata">

**Author:** ![MartinT](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/m/ee7513/32.png) [@MartinT](http://discourse.iapct.org/u/MartinT)\
**Post date:** [May 9, 2019, 8:40pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/12 "2019-05-09T20:40:47Z")

</div>

[Martin Taylor 2019.05.09.16.13]

```
If you call the intended result of an action (bringing a perception

```

toward its reference value) a prediction, I would say that’s a  
strange use of “prediction”. better understanding of what is going  
on. If I decide to go out and do go out, have I predicted that I  
will go out? The Friston “Free Energy” people say exactly that,  
probably for the reasons you suggest below. I would call it at best  
a self-fulfilling prediction, one that comes to pass because of the  
actions of the one who predicts and wouldn’t come to pass in the  
absence of those actions.  
I could be happy with saying that there is a form of prediction  
here, which is a prediction that the Real Reality world will  
continue to act much as it has been acting for a reasonably long  
time. It’s not a prediction that when the cat wants to bat at  
something it will do what is necessary to bat at the thing without  
falling over. But who is predicting? Nobody. Both evolution and  
reorganization work with past data, not predicted future data. The  
“prediction” is simply the working of Natural Law, whether we know  
the law or not.  
Martin

> **···**
>
> On 2019/05/9 3:59 PM, Heather  
> Broccard-Bell ( via csgnet Mailing List) wrote:
> 
> hebell@ucsd.edu
> 
> > ```
> > Sorry, that was meant to go to everyone, not just
> > 
> > ```
> > 
> > Martin 🙂
> 
> > ```
> > On Thu, May 9, 2019 at 12:58
> > 
> > ```
> > 
> > PM Heather Broccard-Bell \<hebell@ucsd.edu \>  
> > wrote:
> 
> > > ```
> > > All right, so what then is the difference
> > > 
> > > ```
> > > 
> > > between operating on a reference signal from an internal  
> > > model, and making a prediction?
> 
> > > ```
> > > Does that not amount to the same thing? 
> > > 
> > > ```
> > > 
> > > After all, the parameters of the internal model are set  
> > > through experience (or evolution – which is some kind of  
> > > sort of larger “experience”). So then the system can be  
> > > biased in a way that allows it to function better than  
> > > ones that aren’t biased that way in a given environment.
> 
> [mmt@mmtaylor.net](mailto:mmt@mmtaylor.net)
> 
> > > > [Martin Taylor 2019.05.09.14.35]
> > > > 
> > > > ```
> > > > On
> > > > 
> > > > ```
> > > > 
> > > > 2019/05/9 1:53 PM, Heather Broccard-Bell wrote:
> 
> > > > > ```
> > > > > I'm still not sure I satisfactorily
> > > > > 
> > > > > ```
> > > > > 
> > > > > answered my own original question, though. And  
> > > > > also, if we can compensate for a predicted  
> > > > > disturbance (even if we can update our  
> > > > > compensation when the compensation is perturbed),  
> > > > > the original reference signal is presumably coming  
> > > > > from some kind of internal model, no? Is this  
> > > > > cool? I thought we were anti-internal model  
> > > > > (except for super sophisticated human cognition  
> > > > > where we do clearly imagine things)? This  
> > > > > suggests cats have one, no?
> 
> > > > ```
> > > > I guess your question is about what the pre-stored
> > > > 
> > > > ```
> > > > 
> > > > energy in the cats muscles is for, and whether it  
> > > > implies prediction of an external disturbance. I don’t  
> > > > think it does. Remember that reference values change,  
> > > > and that reorganization changes parameters and  
> > > > level-to-level interconnection parameters. Maybe the  
> > > > first time the cat ever tried to bat at something it  
> > > > didn’t hit it properly, and maybe it stumbled or fell  
> > > > after the attempt. Nothing of that happened before the  
> > > > cat tried to compensate for a disturbance from  
> > > > outside, so there’s no prediction involved. No  
> > > > subsequent unpredicted disturbance is involved in your  
> > > > question.
> > > > 
> > > > ```
> > > > Everything else is internally generated as changing
> > > > 
> > > > ```
> > > > 
> > > > reference values feed down the levels of control all  
> > > > the way to the individual muscle tension control  
> > > > loops. The feedback effects of the actions generated  
> > > > by the control units whose reference levels were  
> > > > changed are fairly consistent over many attempts at  
> > > > batting at locally moving things (as an observer sees  
> > > > it), so reorganization has the opportunity to build  
> > > > the proper coordinations and sequences of muscle  
> > > > tensions.
> > > > 
> > > > ```
> > > > Yes, there's an internal model. It's in the
> > > > 
> > > > ```
> > > > 
> > > > reorganized connections and parameter settings for the  
> > > > control loops used to do the batting, and part of that  
> > > > is pre-tensioning the muscles both to perform the bat  
> > > > and to reduce the sudden effect of the action until  
> > > > fast normal low-level control loops correct any  
> > > > remaining perceptual errors. I bet you do the same if  
> > > > you pick up a pile of dishes to put them on a shelf.  
> > > > If you started out with slack muscles, you might fall  
> > > > when you picked them up, and when you released them  
> > > > onto the shelf you might fall in the other direction  
> > > > if all the tension was devoted to holding up the  
> > > > plates, rather than to compensate for the change in  
> > > > balance, which you have encountered every time you  
> > > > picked up or released a weight since you were old  
> > > > enough to try.
> > > > 
> > > > ```
> > > > It might be evolution, not primarily reorganization in
> > > > 
> > > > ```
> > > > 
> > > > the individual cat, though, because cats are  
> > > > notoriously good at keeping their attitude with  
> > > > respect to gravity, landing with feet toward the  
> > > > ground if falling from a height, and performing  
> > > > remarkable rapid body contortions while remaining  
> > > > stable.
> > > > 
> > > > ```
> > > > Martin
> > > > 
> > > > ```
> > > > 
> > > > >
> 
> > > > > ```
> > > > > On Thu, May
> > > > > 
> > > > > ```
> > > > > 
> > > > > 9, 2019, 07:18 Warren Mansell \<[wmansell@gmail.com](mailto:wmansell@gmail.com) \>  
> > > > > wrote:
> 
> > > > > > ```
> > > > > > Hurray, PCT wins! But do
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > any of the readers of these papers  
> > > > > > realise?
> 
> > > > > >
> 
> > > > > > ```
> > > > > > On 9 May 2019, at 14:28, Heather
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > Broccard-Bell (hebell@ucsd.edu  
> > > > > > via csgnet Mailing List) \<csgnet@lists.illinois.edu \>  
> > > > > > wrote:
> 
> > > > > > >
> 
> > > > > > > ```
> > > > > > > I suspect that
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > the attached (Aruin, 2003)  
> > > > > > > paper goes some way toward  
> > > > > > > reconciling the “invariant,  
> > > > > > > pre-programmed” feedforward  
> > > > > > > conceptualization with the  
> > > > > > > actual phenomenon: namely,  
> > > > > > > it’s not really invariant (or,  
> > > > > > > well, it’s not invariant in  
> > > > > > > that there is a pre-programmed  
> > > > > > > set of muscles activated in a  
> > > > > > > pre-programmed way). So, I  
> > > > > > > suspect that some of the  
> > > > > > > problem in the “mainstream” is  
> > > > > > > semantic.
> 
> > > > > > > ```
> > > > > > > Anyway, long
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > (~500 ms) stimulation of  
> > > > > > > motor cortex has already  
> > > > > > > demonstrated that “motor  
> > > > > > > output” seems to be about  
> > > > > > > goals, and not specific,  
> > > > > > > muscle-by-muscle motor  
> > > > > > > programs (see Graziano,  
> > > > > > > 2002; attached), and really  
> > > > > > > the only way you could get  
> > > > > > > that to work is hierarchical  
> > > > > > > control with continuous  
> > > > > > > feedback…
> 
> > > > > > > ```
> > > > > > > On Wed,
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > May 8, 2019, 21:16 Martin  
> > > > > > > Taylor \<csgnet@lists.illinois.edu \>  
> > > > > > > wrote:
> 
> > > > > > > > ```
> > > > > > > > [Martin Taylor
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > 2019.05.09.00.09]
> > > > > > > > 
> > > > > > > > > ```
> > > > > > > > > [Rick
> > > > > > > > > 
> > > > > > > > > ```
> > > > > > > > > 
> > > > > > > > > Marken  
> > > > > > > > > 2019-05-08\_17:57:30]
> 
> > > > > > > > >
> 
> > > > > > > > > ```
> > > > > > > > > RM: Some time
> > > > > > > > > 
> > > > > > > > > ```
> > > > > > > > > 
> > > > > > > > > ago Heather  
> > > > > > > > > Broccard-Bell  
> > > > > > > > > asked me what  
> > > > > > > > > the PCT  
> > > > > > > > > explanation  
> > > > > > > > > might be of a  
> > > > > > > > > behavior that  
> > > > > > > > > looks like a  
> > > > > > > > > pretty robust  
> > > > > > > > > example of  
> > > > > > > > > anticipatory (or  
> > > > > > > > > feedforward)  
> > > > > > > > > control. Here’s  
> > > > > > > > > how Heather  
> > > > > > > > > described it to  
> > > > > > > > > me:
> 
> > > > > > > > >
> 
> > > > > > > > > > ```
> > > > > > > > > > HB-B:
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > I was reading  
> > > > > > > > > > about this  
> > > > > > > > > > finding (and  
> > > > > > > > > > perhaps you  
> > > > > > > > > > are already  
> > > > > > > > > > familiar)  
> > > > > > > > > > that, if if  
> > > > > > > > > > you measure  
> > > > > > > > > > muscle  
> > > > > > > > > > activation  
> > > > > > > > > > during  
> > > > > > > > > > behavior, you  
> > > > > > > > > > often see  
> > > > > > > > > > compensatory  
> > > > > > > > > > activation of  
> > > > > > > > > > the axial  
> > > > > > > > > > musculature  
> > > > > > > > > > well before  
> > > > > > > > > > you get  
> > > > > > > > > > activation in  
> > > > > > > > > > the muscles  
> > > > > > > > > > that direct  
> > > > > > > > > > the part of  
> > > > > > > > > > the body that  
> > > > > > > > > > does the thing  
> > > > > > > > > > you’re focused  
> > > > > > > > > > on. For  
> > > > > > > > > > example, they  
> > > > > > > > > > trained cats  
> > > > > > > > > > to bat at a  
> > > > > > > > > > target with  
> > > > > > > > > > their  
> > > > > > > > > > forepaw. \*\* Well  
> > > > > > > > > > before the  
> > > > > > > > > > limb/forepaw  
> > > > > > > > > > muscles are  
> > > > > > > > > > active, there  
> > > > > > > > > > is activation  
> > > > > > > > > > in the trunk  
> > > > > > > > > > musculature,  
> > > > > > > > > > seemingly  
> > > > > > > > > > anticipating  
> > > > > > > > > > the requisite  
> > > > > > > > > > compensatory  
> > > > > > > > > > stabilization  
> > > > > > > > > > that will  
> > > > > > > > > > become  
> > > > > > > > > > necessary when  
> > > > > > > > > > the forepaw is  
> > > > > > > > > > lifted. \*\* I  
> > > > > > > > > > am wondering  
> > > > > > > > > > what a PCT  
> > > > > > > > > > perspective  
> > > > > > > > > > might be on  
> > > > > > > > > > that? What is  
> > > > > > > > > > the relevant  
> > > > > > > > > > controlled  
> > > > > > > > > > variable,  
> > > > > > > > > > since the  
> > > > > > > > > > thing that  
> > > > > > > > > > actually  
> > > > > > > > > > changes  
> > > > > > > > > > sensory input  
> > > > > > > > > > that should  
> > > > > > > > > > activate  
> > > > > > > > > > control  
> > > > > > > > > > architecture  
> > > > > > > > > > hasn’t yet  
> > > > > > > > > > happened? Am  
> > > > > > > > > > I missing  
> > > > > > > > > > something? It  
> > > > > > > > > > appears to be  
> > > > > > > > > > a rather  
> > > > > > > > > > robust  
> > > > > > > > > > finding.[emphasis  
> > > > > > > > > > mine–RM]
> 
> > > > > > > > > …
> 
> > > > > > > > > ```
> > > > > > > > > RM:
> > > > > > > > > 
> > > > > > > > > ```
> > > > > > > > > 
> > > > > > > > > I am posting  
> > > > > > > > > this to you  
> > > > > > > > > experts on PCT  
> > > > > > > > > (with Heather’s  
> > > > > > > > > permission)  
> > > > > > > > > because I think  
> > > > > > > > > this is a very  
> > > > > > > > > interesting  
> > > > > > > > > discovery that  
> > > > > > > > > seems to pose a  
> > > > > > > > > challenge to PCT  
> > > > > > > > > and I would like  
> > > > > > > > > to see what you  
> > > > > > > > > think about  
> > > > > > > > > this.
> 
> > > > > > > > ```
> > > > > > > > Here is section of what I
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > wrote to Heather on this  
> > > > > > > > question April 12.
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > --------
> > > > > > > > 
> > > > > > > > [Here is a] quick and
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > dirty PCT approach. I  
> > > > > > > > start with the intention  
> > > > > > > > to bat at the target,  
> > > > > > > > which would set a  
> > > > > > > > reference for a sequence  
> > > > > > > > that could crudely be  
> > > > > > > > taken as “store energy,  
> > > > > > > > set trigger, wait, release  
> > > > > > > > energy when required”, or  
> > > > > > > > in a more general sense  
> > > > > > > > “Prepare, wait, execute”.  
> > > > > > > > You call the storage  
> > > > > > > > “prestabilizing”, but I  
> > > > > > > > think Powers would have  
> > > > > > > > called that a “dormitive  
> > > > > > > > principle” that just  
> > > > > > > > labels what happens  
> > > > > > > > without in any way  
> > > > > > > > explaining how or why. The  
> > > > > > > > “stabilizing” is postural  
> > > > > > > > control of the normal  
> > > > > > > > kind, the same as would  
> > > > > > > > happen if you pushed the  
> > > > > > > > cat. If you have seen a  
> > > > > > > > video of the “Big Dog”  
> > > > > > > > robot, you have seen this  
> > > > > > > > kind of stabilization.
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > The magician Harry Houdini
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > died because he hadn’t  
> > > > > > > > stored the energy to  
> > > > > > > > resist a blow to his  
> > > > > > > > abdomen when someone hit  
> > > > > > > > him before he was  
> > > > > > > > prepared, which he did by  
> > > > > > > > tensing (supplying energy  
> > > > > > > > to) the stomach muscles.  
> > > > > > > > He had offered a general  
> > > > > > > > challenge that nobody  
> > > > > > > > could hit him there hard  
> > > > > > > > enough to hurt him, but  
> > > > > > > > the hitter was supposed to  
> > > > > > > > do it in a formal kind of  
> > > > > > > > way, when he was prepared.  
> > > > > > > > When the fatal blow was  
> > > > > > > > struck, his muscles had  
> > > > > > > > insufficient stored energy  
> > > > > > > > to oppose the shock energy  
> > > > > > > > in the blow.
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > I think the actual
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > stabilization is simply  
> > > > > > > > the use of some of the  
> > > > > > > > pre-tensioned stored  
> > > > > > > > energy in normal postural  
> > > > > > > > control against a force  
> > > > > > > > that would be  
> > > > > > > > destabilizing, but instead  
> > > > > > > > of the control being  
> > > > > > > > entirely to oppose a  
> > > > > > > > sensed disturbance, it is  
> > > > > > > > part of the output side  
> > > > > > > > support of the sequence  
> > > > > > > > controller. The “bat” is  
> > > > > > > > not simply sending  
> > > > > > > > reference values to  
> > > > > > > > muscles that move the paw  
> > > > > > > > relative to the torso, it  
> > > > > > > > is sending reference  
> > > > > > > > values to all the postural  
> > > > > > > > muscles in a temporal  
> > > > > > > > pattern that has been  
> > > > > > > > reorganized into the  
> > > > > > > > control hierarchy in the  
> > > > > > > > same way as a trained  
> > > > > > > > athlete such as a  
> > > > > > > > ballerina coordinates the  
> > > > > > > > timings and strengths of  
> > > > > > > > her muscle movements so  
> > > > > > > > that what an observer  
> > > > > > > > calls “the” action doesn’t  
> > > > > > > > interfere with her  
> > > > > > > > balance.
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > Anyway, those are my first
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > thoughts on the question,  
> > > > > > > > before breakfast.
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > -------
> > > > > > > > 
> > > > > > > > I haven't considered the
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > problem since then, but I  
> > > > > > > > thought I might offer the  
> > > > > > > > suggestion.
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > The saying "Reculer pour
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > mieux sauter" seems to be  
> > > > > > > > about the same phenomenon.
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > Martin
> > > > > > > > 
> > > > > > > > ```
> 
> > > > > > > \<aruin2003.pdf\>
> 
> > > > > > > \<graziano2002.pdf\>
> 
> > > >
> 
> > >
> 
> > > –  
> > > Heather C.  
> > > Broccard-Bell, Ph.D.
> 
> > >
> 
> > > ```
> > > Adjunct
> > > 
> > > ```
> > > 
> > > Assistant Professor
> 
> > > ```
> > > Department of
> > > 
> > > ```
> > > 
> > > Psychological Sciences
> 
> > > ```
> > > University of
> > > 
> > > ```
> > > 
> > > San Diego
> 
> > >
> 
> > > ```
> > > Visiting
> > > 
> > > ```
> > > 
> > > Scholar
> 
> > > ```
> > > The role
> > > 
> > > ```
> > > 
> > > of noise / variability  
> > > in complex, adaptive  
> > > systems
> 
> > > ```
> > > Nieh
> > > 
> > > ```
> > > 
> > > Honey Bee Lab
> 
> > > ```
> > > Division
> > > 
> > > ```
> > > 
> > > of Biological Sciences;  
> > > Section of Ecology,  
> > > Behavior, and Evolution
> 
> > > ```
> > > University
> > > 
> > > ```
> > > 
> > > of California San Diego
> 
> > > ```
> > > 619.757.4694
> > > 
> > > ```
> 
> > 
> 
> > –  
> > Heather C.  
> > Broccard-Bell, Ph.D.
> 
> > 
> 
> > ```
> > Adjunct
> > 
> > ```
> > 
> > Assistant Professor
> 
> > ```
> > Department
> > 
> > ```
> > 
> > of Psychological Sciences
> 
> > ```
> > University
> > 
> > ```
> > 
> > of San Diego
> 
> > 
> 
> > ```
> > Visiting
> > 
> > ```
> > 
> > Scholar
> 
> > ```
> > The role of
> > 
> > ```
> > 
> > noise / variability in  
> > complex, adaptive systems
> 
> > ```
> > Nieh Honey
> > 
> > ```
> > 
> > Bee Lab
> 
> > ```
> > Division of
> > 
> > ```
> > 
> > Biological Sciences; Section  
> > of Ecology, Behavior, and  
> > Evolution
> 
> > ```
> > University
> > 
> > ```
> > 
> > of California San Diego
> 
> > ```
> > 619.757.4694
> > 
> > ```

---

<div class="post-metadata">

**Author:** ![Heather\_Broccard-Bel](http://discourse.iapct.org/user_avatar/discourse.iapct.org/heather_broccard-bel/32/43_2.png) [@Heather\_Broccard-Bel](http://discourse.iapct.org/u/Heather_Broccard-Bel)\
**Post date:** [May 9, 2019, 8:49pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/13 "2019-05-09T20:49:39Z")

</div>

I agree, nobody is actively making a prediction, but the system is tuned to perform better in the world as it as previously experienced it (as stated), because mostly this works out – because often the world is kind of consistent. What makes a prediction different, and what then does it mean to make a prediction? Does a prediction have to be a fully-formed set of anticipated data? I think I am not understanding what makes “prediction” different from “bias based on past experience”.

> **···**
>
> Heather C. Broccard-Bell, Ph.D.
> 
> Adjunct Assistant Professor
> 
> Department of Psychological Sciences
> 
> University of San Diego
> 
> Visiting Scholar
> 
> The role of noise / variability in complex, adaptive systems
> 
> Nieh Honey Bee Lab
> 
> Division of Biological Sciences; Section of Ecology, Behavior, and Evolution
> 
> University of California San Diego
> 
> 619.757.4694

---

<div class="post-metadata">

**Author:** ![bleach](http://discourse.iapct.org/user_avatar/discourse.iapct.org/bleach/32/51_2.png) [@bleach](http://discourse.iapct.org/u/bleach)\
**Post date:** [May 9, 2019, 9:33pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/14 "2019-05-09T21:33:46Z")

</div>

Heather, don’t make the mistake of presuming that I am somehow an  
authority on PCT here!

```
  There is not much that applied PCT can predict in a formal manner

```

yet. Bill Powers made quite a few predictions that turned out to  
be quite good when he developed the theory. The hierarchy is  
pretty strongly supported by the actual measured time delays for  
various kinds of behavior changes is an example. Some PCT  
stimulators have predicted a subject’s performance on a new  
“tracking task” with remarkable accuracy.

```
  One difficulty that I perceive is that many the behavioral

```

science arena do often make pretty accurate predictions but their  
‘school of behavioral science’ actually does not provide any  
support for (or for how) they reached their conclusions. Another  
way of talking about what I’m trying to say is that these  
successful practitioners (usually Psychiatrists) are using some  
sort of a model in their own mind to generate their conclusions  
but that model has no support in their school of the science.

```
  An additional difference is that in PCT there is no such thing as

```

an ‘outlier.’ If an outlier shows up then there is something  
wrong with the experiment or there is something wrong with the  
theory (or both).

```
  There is a subtle but vitally important difference between seeing

```

that an environmental disturbance causes a behavior change and  
seeing that a control system changes behavior (output) to control  
for disturbances to a perception.

```
  I don't know if this helps or hinders. The ability to use PCT in

```

applied science is in its infancy.

bill

> **···**
>
> On 5/9/19 1:17 PM, Heather  
> Broccard-Bell ( via csgnet Mailing List) wrote:
> 
> hebell@ucsd.edu
> 
> > ```
> > I see that according to Bill Leach, internal models
> > 
> > ```
> > 
> > are allowed. So then the question becomes, does the PCT  
> > interpretation generate any predictions that are meaningfully  
> > different from the “mainstream” approaches would predict?
> 
> > ```
> > On Thu, May 9, 2019 at 10:53
> > 
> > ```
> > 
> > AM Heather Broccard-Bell [hebell@ucsd.edu](mailto:hebell@ucsd.edu) wrote:
> 
> > > ```
> > > I'm still not sure I satisfactorily answered
> > > 
> > > ```
> > > 
> > > my own original question, though. And also, if we can  
> > > compensate for a predicted disturbance (even if we can  
> > > update our compensation when the compensation is perturbed),  
> > > the original reference signal is presumably coming from some  
> > > kind of internal model, no? Is this cool? I thought we  
> > > were anti-internal model (except for super sophisticated  
> > > human cognition where we do clearly imagine things)? This  
> > > suggests cats have one, no?
> 
> > > ```
> > > On Thu, May 9, 2019,
> > > 
> > > ```
> > > 
> > > 07:18 Warren Mansell \<[wmansell@gmail.com](mailto:wmansell@gmail.com) \>  
> > > wrote:
> 
> > > > ```
> > > > Hurray, PCT wins! But do any of the
> > > > 
> > > > ```
> > > > 
> > > > readers of these papers realise?
> 
> > > >
> 
> > > > ```
> > > > On 9 May 2019, at 14:28, Heather Broccard-Bell (hebell@ucsd.edu via
> > > > 
> > > > ```
> > > > 
> > > > csgnet Mailing List) \<csgnet@lists.illinois.edu \>  
> > > > wrote:
> 
> > > > >
> 
> > > > > ```
> > > > > I suspect that the
> > > > > 
> > > > > ```
> > > > > 
> > > > > attached (Aruin, 2003) paper goes some  
> > > > > way toward reconciling the “invariant,  
> > > > > pre-programmed” feedforward  
> > > > > conceptualization with the actual  
> > > > > phenomenon: namely, it’s not really  
> > > > > invariant (or, well, it’s not invariant  
> > > > > in that there is a pre-programmed set of  
> > > > > muscles activated in a pre-programmed  
> > > > > way). So, I suspect that some of the  
> > > > > problem in the “mainstream” is semantic.
> 
> > > > > ```
> > > > > Anyway, long (~500 ms)
> > > > > 
> > > > > ```
> > > > > 
> > > > > stimulation of motor cortex has  
> > > > > already demonstrated that “motor  
> > > > > output” seems to be about goals, and  
> > > > > not specific, muscle-by-muscle motor  
> > > > > programs (see Graziano, 2002;  
> > > > > attached), and really the only way you  
> > > > > could get that to work is hierarchical  
> > > > > control with continuous feedback…
> 
> > > > > ```
> > > > > On
> > > > > 
> > > > > ```
> > > > > 
> > > > > Wed, May 8, 2019, 21:16 Martin Taylor  
> > > > > \<csgnet@lists.illinois.edu \>  
> > > > > wrote:
> 
> > > > > > ```
> > > > > > [Martin Taylor
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > 2019.05.09.00.09]
> > > > > > 
> > > > > > > ```
> > > > > > > [Rick Marken
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > 2019-05-08\_17:57:30]
> 
> > > > > > >
> 
> > > > > > > ```
> > > > > > > RM: Some time ago
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > Heather Broccard-Bell  
> > > > > > > asked me what the PCT  
> > > > > > > explanation might be of a  
> > > > > > > behavior that looks like a  
> > > > > > > pretty robust example of  
> > > > > > > anticipatory (or  
> > > > > > > feedforward) control.  
> > > > > > > Here’s how Heather  
> > > > > > > described it to me:
> 
> > > > > > >
> 
> > > > > > > > ```
> > > > > > > > HB-B:
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > I was reading about this  
> > > > > > > > finding (and perhaps you  
> > > > > > > > are already familiar)  
> > > > > > > > that, if if you measure  
> > > > > > > > muscle activation during  
> > > > > > > > behavior, you often see  
> > > > > > > > compensatory activation  
> > > > > > > > of the axial musculature  
> > > > > > > > well before you get  
> > > > > > > > activation in the  
> > > > > > > > muscles that direct the  
> > > > > > > > part of the body that  
> > > > > > > > does the thing you’re  
> > > > > > > > focused on. For  
> > > > > > > > example, they trained  
> > > > > > > > cats to bat at a target  
> > > > > > > > with their forepaw. \*\* Well  
> > > > > > > > before the  
> > > > > > > > limb/forepaw muscles  
> > > > > > > > are active, there is  
> > > > > > > > activation in the  
> > > > > > > > trunk musculature,  
> > > > > > > > seemingly anticipating  
> > > > > > > > the requisite  
> > > > > > > > compensatory  
> > > > > > > > stabilization that  
> > > > > > > > will become necessary  
> > > > > > > > when the forepaw is  
> > > > > > > > lifted. \*\* I am  
> > > > > > > > wondering what a PCT  
> > > > > > > > perspective might be on  
> > > > > > > > that? What is the  
> > > > > > > > relevant controlled  
> > > > > > > > variable, since the  
> > > > > > > > thing that actually  
> > > > > > > > changes sensory input  
> > > > > > > > that should activate  
> > > > > > > > control architecture  
> > > > > > > > hasn’t yet happened? Am  
> > > > > > > > I missing something? It  
> > > > > > > > appears to be a rather  
> > > > > > > > robust finding.[emphasis  
> > > > > > > > mine–RM]
> 
> > > > > > > …
> 
> > > > > > > ```
> > > > > > > RM: I am
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > posting this to you  
> > > > > > > experts on PCT (with  
> > > > > > > Heather’s permission)  
> > > > > > > because I think this is a  
> > > > > > > very interesting discovery  
> > > > > > > that seems to pose a  
> > > > > > > challenge to PCT and I  
> > > > > > > would like to see what you  
> > > > > > > think about this.
> 
> > > > > > ```
> > > > > > Here is section of what I wrote to
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > Heather on this question April 12.
> > > > > > 
> > > > > > ```
> > > > > > --------
> > > > > > 
> > > > > > [Here is a] quick and dirty PCT
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > approach. I start with the intention  
> > > > > > to bat at the target, which would  
> > > > > > set a reference for a sequence that  
> > > > > > could crudely be taken as “store  
> > > > > > energy, set trigger, wait, release  
> > > > > > energy when required”, or in a more  
> > > > > > general sense “Prepare, wait,  
> > > > > > execute”. You call the storage  
> > > > > > “prestabilizing”, but I think Powers  
> > > > > > would have called that a “dormitive  
> > > > > > principle” that just labels what  
> > > > > > happens without in any way  
> > > > > > explaining how or why. The  
> > > > > > “stabilizing” is postural control of  
> > > > > > the normal kind, the same as would  
> > > > > > happen if you pushed the cat. If you  
> > > > > > have seen a video of the “Big Dog”  
> > > > > > robot, you have seen this kind of  
> > > > > > stabilization.
> > > > > > 
> > > > > > ```
> > > > > > The magician Harry Houdini died
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > because he hadn’t stored the energy  
> > > > > > to resist a blow to his abdomen when  
> > > > > > someone hit him before he was  
> > > > > > prepared, which he did by tensing  
> > > > > > (supplying energy to) the stomach  
> > > > > > muscles. He had offered a general  
> > > > > > challenge that nobody could hit him  
> > > > > > there hard enough to hurt him, but  
> > > > > > the hitter was supposed to do it in  
> > > > > > a formal kind of way, when he was  
> > > > > > prepared. When the fatal blow was  
> > > > > > struck, his muscles had insufficient  
> > > > > > stored energy to oppose the shock  
> > > > > > energy in the blow.
> > > > > > 
> > > > > > ```
> > > > > > I think the actual stabilization is
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > simply the use of some of the  
> > > > > > pre-tensioned stored energy in  
> > > > > > normal postural control against a  
> > > > > > force that would be destabilizing,  
> > > > > > but instead of the control being  
> > > > > > entirely to oppose a sensed  
> > > > > > disturbance, it is part of the  
> > > > > > output side support of the sequence  
> > > > > > controller. The “bat” is not simply  
> > > > > > sending reference values to muscles  
> > > > > > that move the paw relative to the  
> > > > > > torso, it is sending reference  
> > > > > > values to all the postural muscles  
> > > > > > in a temporal pattern that has been  
> > > > > > reorganized into the control  
> > > > > > hierarchy in the same way as a  
> > > > > > trained athlete such as a ballerina  
> > > > > > coordinates the timings and  
> > > > > > strengths of her muscle movements so  
> > > > > > that what an observer calls “the”  
> > > > > > action doesn’t interfere with her  
> > > > > > balance.
> > > > > > 
> > > > > > ```
> > > > > > Anyway, those are my first thoughts
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > on the question, before breakfast.
> > > > > > 
> > > > > > ```
> > > > > > -------
> > > > > > 
> > > > > > I haven't considered the problem
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > since then, but I thought I might  
> > > > > > offer the suggestion.
> > > > > > 
> > > > > > ```
> > > > > > The saying "Reculer pour mieux
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > sauter" seems to be about the same  
> > > > > > phenomenon.
> > > > > > 
> > > > > > ```
> > > > > > Martin
> > > > > > 
> > > > > > ```
> 
> > > > > \<aruin2003.pdf\>
> 
> > > > > \<graziano2002.pdf\>
> 
> > 
> 
> > –  
> > Heather C.  
> > Broccard-Bell, Ph.D.
> 
> > 
> 
> > ```
> > Adjunct
> > 
> > ```
> > 
> > Assistant Professor
> 
> > ```
> > Department
> > 
> > ```
> > 
> > of Psychological Sciences
> 
> > ```
> > University
> > 
> > ```
> > 
> > of San Diego
> 
> > 
> 
> > ```
> > Visiting
> > 
> > ```
> > 
> > Scholar
> 
> > ```
> > The role of
> > 
> > ```
> > 
> > noise / variability in  
> > complex, adaptive systems
> 
> > ```
> > Nieh Honey Bee
> > 
> > ```
> > 
> > Lab
> 
> > ```
> > Division of
> > 
> > ```
> > 
> > Biological Sciences; Section  
> > of Ecology, Behavior, and  
> > Evolution
> 
> > ```
> > University of
> > 
> > ```
> > 
> > California San Diego
> 
> > ```
> > 619.757.4694
> > 
> > ```

---

<div class="post-metadata">

**Author:** ![Heather\_Broccard-Bel](http://discourse.iapct.org/user_avatar/discourse.iapct.org/heather_broccard-bel/32/43_2.png) [@Heather\_Broccard-Bel](http://discourse.iapct.org/u/Heather_Broccard-Bel)\
**Post date:** [May 9, 2019, 9:56pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/15 "2019-05-09T21:56:01Z")

</div>

Indeed, it is in its infancy, and I wish more people would work on it 🙂

> **···**
>
> Heather C. Broccard-Bell, Ph.D.
> 
> Adjunct Assistant Professor
> 
> Department of Psychological Sciences
> 
> University of San Diego
> 
> Visiting Scholar
> 
> The role of noise / variability in complex, adaptive systems
> 
> Nieh Honey Bee Lab
> 
> Division of Biological Sciences; Section of Ecology, Behavior, and Evolution
> 
> University of California San Diego
> 
> 619.757.4694

---

<div class="post-metadata">

**Author:** ![bleach](http://discourse.iapct.org/user_avatar/discourse.iapct.org/bleach/32/51_2.png) [@bleach](http://discourse.iapct.org/u/bleach)\
**Post date:** [May 9, 2019, 10:02pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/16 "2019-05-09T22:02:30Z")

</div>

Feedforward in engineering control, is model based. The model is  
often implicit, as in experience where the control system retains  
information concerning how well it controlled a particular sensed  
parameter and other related parameters. The easiest example that  
I can think of, is the room heating system. In such a system, if  
you add sensors to monitor outside temperature, status of doors  
and windows, and the number of occupants; and record the amount of  
error in maintaining the room temperature, then you can compute  
anticipatory actions to minimize control error. The system might  
start the heater before the “set temperature” by raising the  
controller reference if the door to the outside was opened and the  
outside temperature is very low.

```
  There is, in my mind, no reason why experience should not allow

```

for similar action in living systems. Indeed, even Martin’s  
example of sequencing involves a model in that the sequence **is**  
a model. In a specific subject that model was either constructed  
or inherited but at some point, maybe eons ago it was  
constructed. Some form or reorganization was involved in the  
construction to correct for uncontrolled or poorly controlled  
error.

```
  "Pre-action tensioning" is a fine label for the sequence step but

```

keep in mind that the whole sequence is based upon _anticipating_  
the need to run the sequence to ensure satisfactory control of  
perception including an expected future perception.

bill

> **···**
>
> On 5/9/19 1:54 PM, “Erling Jorgensen”  
> ( via csgnet Mailing List) wrote:
> 
> [EJorgensen@riverbendcmhc.org](mailto:EJorgensen@riverbendcmhc.org)
> 
> > [From Erling Jorgensen (2019.05.09 1530 EDT)]
> 
> > ```
> > EJ: To say "internal models" still requires some notion of
> > 
> > ```
> > 
> > mechanism, so until that is specified a little better, in my  
> > mind the term remains ‘hand waving’. It seems like  
> > “pre-action tensioning” is a valid shorthand description of  
> > the phenomenon, for which “anticipatory stabilization” had  
> > been proposed as an explanation.
> 
> > 
> 
> > ```
> > EJ: I rather like Martin's proposal for controlling a
> > 
> > ```
> > 
> > prior stage in a sequence. I think of the similarity to how  
> > Segway machines are operated, as an analogue for human  
> > walking. Before an actual step is taken, there is leaning  
> > forward and the center of gravity shifts. I wonder whether  
> > that is akin to the “activation in the trunk musculature” that  
> > is measured before a cat’s forepaw is actually lifted. But  
> > “tensioning a muscle” is still a present moment control  
> > process, via equal increase of force to both sides of  
> > an opponent-process muscle. It requires neither anticipatory  
> > effects nor discernible movement.
> 
> > 
> 
> > ```
> > EJ: I appreciate the way Heather is fashioning the
> > 
> > ```
> > 
> > question, in terms of “meaningfully different predictions”.  
> > The standard PCT model says output is generated by error  
> > already occurring, which means either a disturbance moved an  
> > existing perception away from its preferred value, or a change  
> > in reference happened toward which the perception now moves.  
> > Feedforward effects are a different model, and it is not yet  
> > clear whether PCT has yet had to make much use of such  
> > mechanisms.
> 
> > Erling
> 
> > 
> 
> > _ **Confidentiality:** _\*  
> > This message is intended only for the addressee, and  
> > may contain information that is privileged and  
> > confidential under HIPAA, 42CFR Part 2, and/or other  
> > applicable State and Federal laws. If you are not the  
> > addressee, or the employer or agent responsible for  
> > delivering the message to the addressee, any  
> > dissemination, distribution or copying of this  
> > communication is strictly prohibited. \*\* If you have  
> > received this in error, please notify the sender  
> > immediately and delete the material from your  
> > computer. Thank you for your cooperation.\*\*\*
> 
> > _ **Please also note:** _\*  
> > Under 42 CFR part 2 you are prohibited from making  
> > any further disclosure of information that  
> > identifies an individual as having or having had a  
> > substance use disorder unless it is expressly  
> > permitted by the written consent of the individual  
> > whose information is being disclosed or as otherwise  
> > permitted by 42 CFR Part 2.\*
> 
> > ```
> > >>> "Heather Broccard-Bell" ( via
> > 
> > ```
> > 
> > csgnet Mailing List) 5/9/2019 3:17 PM \>\>\>
> > 
> > ```
> > * **CAUTION** - This is an
> > 
> > ```
> > 
> > EXTERNAL email - DO NOT open attachments or links in  
> > unexpected emails or from unknown senders \*
> 
> > ```
> > I see that according to Bill Leach, internal
> > 
> > ```
> > 
> > models are allowed. So then the question becomes, does the  
> > PCT interpretation generate any predictions that are  
> > meaningfully different from the “mainstream” approaches  
> > would predict?
> 
> > 
> 
> > ```
> > On Thu, May 9, 2019 at
> > 
> > ```
> > 
> > 10:53 AM Heather Broccard-Bell \<hebell@ucsd.edu \>  
> > wrote:
> 
> > > ```
> > > I'm still not sure I satisfactorily
> > > 
> > > ```
> > > 
> > > answered my own original question, though. And also,  
> > > if we can compensate for a predicted disturbance (even  
> > > if we can update our compensation when the  
> > > compensation is perturbed), the original reference  
> > > signal is presumably coming from some kind of internal  
> > > model, no? Is this cool? I thought we were  
> > > anti-internal model (except for super sophisticated  
> > > human cognition where we do clearly imagine things)?  
> > > This suggests cats have one, no?
> 
> > > ```
> > > On Thu, May 9,
> > > 
> > > ```
> > > 
> > > 2019, 07:18 Warren Mansell \<[wmansell@gmail.com](mailto:wmansell@gmail.com) \>  
> > > wrote:
> 
> > > > ```
> > > > Hurray, PCT wins! But do any of
> > > > 
> > > > ```
> > > > 
> > > > the readers of these papers realise?
> 
> > > >
> 
> > > > ```
> > > > On 9 May 2019, at 14:28, Heather
> > > > 
> > > > ```
> > > > 
> > > > Broccard-Bell (hebell@ucsd.edu  
> > > > via csgnet Mailing List) \<csgnet@lists.illinois.edu \>  
> > > > wrote:
> 
> > > > >
> 
> > > > > ```
> > > > > I suspect that the
> > > > > 
> > > > > ```
> > > > > 
> > > > > attached (Aruin, 2003) paper goes  
> > > > > some way toward reconciling the  
> > > > > “invariant, pre-programmed”  
> > > > > feedforward conceptualization with  
> > > > > the actual phenomenon: namely,  
> > > > > it’s not really invariant (or,  
> > > > > well, it’s not invariant in that  
> > > > > there is a pre-programmed set of  
> > > > > muscles activated in a  
> > > > > pre-programmed way). So, I suspect  
> > > > > that some of the problem in the  
> > > > > “mainstream” is semantic.
> 
> > > > > ```
> > > > > Anyway, long (~500
> > > > > 
> > > > > ```
> > > > > 
> > > > > ms) stimulation of motor cortex  
> > > > > has already demonstrated that  
> > > > > “motor output” seems to be about  
> > > > > goals, and not specific,  
> > > > > muscle-by-muscle motor programs  
> > > > > (see Graziano, 2002; attached),  
> > > > > and really the only way you  
> > > > > could get that to work is  
> > > > > hierarchical control with  
> > > > > continuous feedback…
> 
> > > > > ```
> > > > > On
> > > > > 
> > > > > ```
> > > > > 
> > > > > Wed, May 8, 2019, 21:16 Martin  
> > > > > Taylor \<csgnet@lists.illinois.edu \>  
> > > > > wrote:
> 
> > > > > > ```
> > > > > > [Martin
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > Taylor 2019.05.09.00.09]
> > > > > > 
> > > > > > > ```
> > > > > > > [Rick
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > Marken  
> > > > > > > 2019-05-08\_17:57:30]
> 
> > > > > > >
> 
> > > > > > > ```
> > > > > > > RM: Some time ago
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > Heather  
> > > > > > > Broccard-Bell asked  
> > > > > > > me what the PCT  
> > > > > > > explanation might be  
> > > > > > > of a behavior that  
> > > > > > > looks like a pretty  
> > > > > > > robust example of  
> > > > > > > anticipatory (or  
> > > > > > > feedforward)  
> > > > > > > control. Here’s how  
> > > > > > > Heather described it  
> > > > > > > to me:
> 
> > > > > > >
> 
> > > > > > > > ```
> > > > > > > > HB-B: I
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > was reading about  
> > > > > > > > this finding (and  
> > > > > > > > perhaps you are  
> > > > > > > > already familiar)  
> > > > > > > > that, if if you  
> > > > > > > > measure muscle  
> > > > > > > > activation during  
> > > > > > > > behavior, you  
> > > > > > > > often see  
> > > > > > > > compensatory  
> > > > > > > > activation of the  
> > > > > > > > axial musculature  
> > > > > > > > well before you  
> > > > > > > > get activation in  
> > > > > > > > the muscles that  
> > > > > > > > direct the part of  
> > > > > > > > the body that does  
> > > > > > > > the thing you’re  
> > > > > > > > focused on. For  
> > > > > > > > example, they  
> > > > > > > > trained cats to  
> > > > > > > > bat at a target  
> > > > > > > > with their  
> > > > > > > > forepaw. \*\* Well  
> > > > > > > > before the  
> > > > > > > > limb/forepaw  
> > > > > > > > muscles are  
> > > > > > > > active, there is  
> > > > > > > > activation in  
> > > > > > > > the trunk  
> > > > > > > > musculature,  
> > > > > > > > seemingly  
> > > > > > > > anticipating the  
> > > > > > > > requisite  
> > > > > > > > compensatory  
> > > > > > > > stabilization  
> > > > > > > > that will become  
> > > > > > > > necessary when  
> > > > > > > > the forepaw is  
> > > > > > > > lifted.\*\* I  
> > > > > > > > am wondering what  
> > > > > > > > a PCT perspective  
> > > > > > > > might be on that?  
> > > > > > > > What is the  
> > > > > > > > relevant  
> > > > > > > > controlled  
> > > > > > > > variable, since  
> > > > > > > > the thing that  
> > > > > > > > actually changes  
> > > > > > > > sensory input that  
> > > > > > > > should activate  
> > > > > > > > control  
> > > > > > > > architecture  
> > > > > > > > hasn’t yet  
> > > > > > > > happened? Am I  
> > > > > > > > missing something?  
> > > > > > > > It appears to be a  
> > > > > > > > rather robust  
> > > > > > > > finding.[emphasis  
> > > > > > > > mine–RM]
> 
> > > > > > > …
> 
> > > > > > > ```
> > > > > > > RM: I
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > am posting this to  
> > > > > > > you experts on PCT  
> > > > > > > (with Heather’s  
> > > > > > > permission) because  
> > > > > > > I think this is a  
> > > > > > > very interesting  
> > > > > > > discovery that seems  
> > > > > > > to pose a challenge  
> > > > > > > to PCT and I would  
> > > > > > > like to see what you  
> > > > > > > think about this.
> 
> > > > > > ```
> > > > > > Here is section of what I
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > wrote to Heather on this  
> > > > > > question April 12.
> > > > > > 
> > > > > > ```
> > > > > > --------
> > > > > > 
> > > > > > [Here is a] quick and dirty
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > PCT approach. I start with the  
> > > > > > intention to bat at the  
> > > > > > target, which would set a  
> > > > > > reference for a sequence that  
> > > > > > could crudely be taken as  
> > > > > > “store energy, set trigger,  
> > > > > > wait, release energy when  
> > > > > > required”, or in a more  
> > > > > > general sense “Prepare, wait,  
> > > > > > execute”. You call the storage  
> > > > > > “prestabilizing”, but I think  
> > > > > > Powers would have called that  
> > > > > > a “dormitive principle” that  
> > > > > > just labels what happens  
> > > > > > without in any way explaining  
> > > > > > how or why. The “stabilizing”  
> > > > > > is postural control of the  
> > > > > > normal kind, the same as would  
> > > > > > happen if you pushed the cat.  
> > > > > > If you have seen a video of  
> > > > > > the “Big Dog” robot, you have  
> > > > > > seen this kind of  
> > > > > > stabilization.
> > > > > > 
> > > > > > ```
> > > > > > The magician Harry Houdini
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > died because he hadn’t stored  
> > > > > > the energy to resist a blow to  
> > > > > > his abdomen when someone hit  
> > > > > > him before he was prepared,  
> > > > > > which he did by tensing  
> > > > > > (supplying energy to) the  
> > > > > > stomach muscles. He had  
> > > > > > offered a general challenge  
> > > > > > that nobody could hit him  
> > > > > > there hard enough to hurt him,  
> > > > > > but the hitter was supposed to  
> > > > > > do it in a formal kind of way,  
> > > > > > when he was prepared. When the  
> > > > > > fatal blow was struck, his  
> > > > > > muscles had insufficient  
> > > > > > stored energy to oppose the  
> > > > > > shock energy in the blow.
> > > > > > 
> > > > > > ```
> > > > > > I think the actual
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > stabilization is simply the  
> > > > > > use of some of the  
> > > > > > pre-tensioned stored energy in  
> > > > > > normal postural control  
> > > > > > against a force that would be  
> > > > > > destabilizing, but instead of  
> > > > > > the control being entirely to  
> > > > > > oppose a sensed disturbance,  
> > > > > > it is part of the output side  
> > > > > > support of the sequence  
> > > > > > controller. The “bat” is not  
> > > > > > simply sending reference  
> > > > > > values to muscles that move  
> > > > > > the paw relative to the torso,  
> > > > > > it is sending reference values  
> > > > > > to all the postural muscles in  
> > > > > > a temporal pattern that has  
> > > > > > been reorganized into the  
> > > > > > control hierarchy in the same  
> > > > > > way as a trained athlete such  
> > > > > > as a ballerina coordinates the  
> > > > > > timings and strengths of her  
> > > > > > muscle movements so that what  
> > > > > > an observer calls “the” action  
> > > > > > doesn’t interfere with her  
> > > > > > balance.
> > > > > > 
> > > > > > ```
> > > > > > Anyway, those are my first
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > thoughts on the question,  
> > > > > > before breakfast.
> > > > > > 
> > > > > > ```
> > > > > > -------
> > > > > > 
> > > > > > I haven't considered the
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > problem since then, but I  
> > > > > > thought I might offer the  
> > > > > > suggestion.
> > > > > > 
> > > > > > ```
> > > > > > The saying "Reculer pour mieux
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > sauter" seems to be about the  
> > > > > > same phenomenon.
> > > > > > 
> > > > > > ```
> > > > > > Martin
> > > > > > 
> > > > > > ```
> 
> > > > > \<aruin2003.pdf\>
> 
> > > > > \<graziano2002.pdf\>
> 
> > 
> 
> > 
> 
> > –
> 
> > ```
> > Heather C.
> > 
> > ```
> > 
> > Broccard-Bell, Ph.D.
> 
> > 
> 
> > ```
> > Adjunct
> > 
> > ```
> > 
> > Assistant Professor
> 
> > ```
> > Department of
> > 
> > ```
> > 
> > Psychological Sciences
> 
> > ```
> > University of
> > 
> > ```
> > 
> > San Diego
> 
> > 
> 
> > ```
> > Visiting
> > 
> > ```
> > 
> > Scholar
> 
> > ```
> > The role
> > 
> > ```
> > 
> > of noise / variability  
> > in complex, adaptive  
> > systems
> 
> > ```
> > Nieh
> > 
> > ```
> > 
> > Honey Bee Lab
> 
> > ```
> > Division
> > 
> > ```
> > 
> > of Biological Sciences;  
> > Section of Ecology,  
> > Behavior, and Evolution
> 
> > ```
> > University
> > 
> > ```
> > 
> > of California San Diego
> 
> > ```
> > 619.757.4694
> > 
> > ```
> 
> hebell@ucsd.edu[csgnet@lists.illinois.edu](mailto:csgnet@lists.illinois.edu)

---

<div class="post-metadata">

**Author:** ![bleach](http://discourse.iapct.org/user_avatar/discourse.iapct.org/bleach/32/51_2.png) [@bleach](http://discourse.iapct.org/u/bleach)\
**Post date:** [May 9, 2019, 10:39pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/17 "2019-05-09T22:39:54Z")

</div>

> I agree, nobody is actively making a prediction, but the system is tuned to perform better in the world as it as previously experienced it (as stated), because mostly this works out -- because often the world is kind of consistent. What makes a prediction different, and what then does it mean to make a prediction? Does a prediction have to be a fully-formed set of anticipated data? I think I am not understanding what makes "prediction" different from "bias based on past experience".

I suggest that "bias based on past experience" is the basis for all prediction with respect to control system operation. The term prediction also encompasses things like "the world is going to end in 12 years" which I think it is reasonable to assume is not experience based.

bill

> > [Martin Taylor 2019.05.09.16.13]
> > 
> > > Sorry, that was meant to go to everyone, not just Martin 🙂
> > > 
> > > > All right, so what then is the difference between operating on a reference signal from an internal model, and making a prediction?
> > 
> > If you call the intended result of an action (bringing a perception toward its reference value) a prediction, I would say that's a strange use of "prediction". better understanding of what is going on. If I decide to go out and do go out, have I predicted that I will go out? The Friston "Free Energy" people say exactly that, probably for the reasons you suggest below. I would call it at best a self-fulfilling prediction, one that comes to pass because of the actions of the one who predicts and wouldn't come to pass in the absence of those actions.
> > 
> > > > Does that not amount to the same thing? After all, the parameters of the internal model are set through experience (or evolution -- which is some kind of sort of larger "experience"). So then the system can be biased in a way that allows it to function better than ones that aren't biased that way in a given environment.
> > 
> > I could be happy with saying that there is a form of prediction here, which is a prediction that the Real Reality world will continue to act much as it has been acting for a reasonably long time. It's not a prediction that when the cat wants to bat at something it will do what is necessary to bat at the thing without falling over. But who is predicting? Nobody. Both evolution and reorganization work with past data, not predicted future data. The "prediction" is simply the working of Natural Law, whether we know the law or not.
> > 
> > Martin
> > 
> > > > > [Martin Taylor 2019.05.09.14.35]
> > > > > 
> > > > > > I'm still not sure I satisfactorily answered my own original question, though. And also, if we can compensate for a predicted disturbance (even if we can update our compensation when the compensation is perturbed), the original reference signal is presumably coming from some kind of internal model, no? Is this cool? I thought we were anti-internal model (except for super sophisticated human cognition where we do clearly imagine things)? This suggests cats have one, no?
> > > > > 
> > > > > I guess your question is about what the pre-stored energy in the cats muscles is for, and whether it implies prediction of an external disturbance. I don't think it does. Remember that reference values change, and that reorganization changes parameters and level-to-level interconnection parameters. Maybe the first time the cat ever tried to bat at something it didn't hit it properly, and maybe it stumbled or fell after the attempt. Nothing of that happened before the cat tried to compensate for a disturbance from outside, so there's no prediction involved. No subsequent unpredicted disturbance is involved in your question.
> > > > > 
> > > > > Everything else is internally generated as changing reference values feed down the levels of control all the way to the individual muscle tension control loops. The feedback effects of the actions generated by the control units whose reference levels were changed are fairly consistent over many attempts at batting at locally moving things (as an observer sees it), so reorganization has the opportunity to build the proper coordinations and sequences of muscle tensions.
> > > > > 
> > > > > Yes, there's an internal model. It's in the reorganized connections and parameter settings for the control loops used to do the batting, and part of that is pre-tensioning the muscles both to perform the bat and to reduce the sudden effect of the action until fast normal low-level control loops correct any remaining perceptual errors. I bet you do the same if you pick up a pile of dishes to put them on a shelf. If you started out with slack muscles, you might fall when you picked them up, and when you released them onto the shelf you might fall in the other direction if all the tension was devoted to holding up the plates, rather than to compensate for the change in balance, which you have encountered every time you picked up or released a weight since you were old enough to try.
> > > > > 
> > > > > It might be evolution, not primarily reorganization in the individual cat, though, because cats are notoriously good at keeping their attitude with respect to gravity, landing with feet toward the ground if falling from a height, and performing remarkable rapid body contortions while remaining stable.
> > > > > 
> > > > > Martin
> > > > > 
> > > > > > > Hurray, PCT wins! But do any of the readers of these papers realise?
> > > > > > > 
> > > > > > > > I suspect that the attached (Aruin, 2003) paper goes some way toward reconciling the "invariant, pre-programmed" feedforward conceptualization with the actual phenomenon: namely, it's not really invariant (or, well, it's not invariant in that there is a pre-programmed set of muscles activated in a pre-programmed way). So, I suspect that some of the problem in the "mainstream" is semantic.  
> > > > > > > > Anyway, long (~500 ms) stimulation of motor cortex has already demonstrated that "motor output" seems to be about goals, and not specific, muscle-by-muscle motor programs (see Graziano, 2002; attached), and really the only way you could get that to work is hierarchical control with continuous feedback...
> > > > > > > > 
> > > > > > > > > [Martin Taylor 2019.05.09.00.09]
> > > > > > > > > 
> > > > > > > > > > [Rick Marken 2019-05-08\_17:57:30]  
> > > > > > > > > > RM: Some time ago Heather Broccard-Bell asked me what the PCT explanation might be of a behavior that looks like a pretty robust example of anticipatory (or feedforward) control. Here's how Heather described it to me:
> > > > > > > > > > 
> > > > > > > > > > > HB-B: I was reading about this finding (and perhaps you are already familiar) that, if if you measure muscle activation during behavior, you often see compensatory activation of the axial musculature well before you get activation in the muscles that direct the part of the body that does the thing you're focused on. For example, they trained cats to bat at a target with their forepaw. Well before the limb/forepaw muscles are active, there is activation in the trunk musculature, seemingly anticipating the requisite compensatory stabilization that will become necessary when the forepaw is lifted. I am wondering what a PCT perspective might be on that? What is the relevant controlled variable, since the thing that actually changes sensory input that should activate control architecture hasn't yet happened? Am I missing something? It appears to be a rather robust finding.[emphasis mine--RM]
> > > > > > > > > > 
> > > > > > > > > > ...

RM: I am posting this to you experts on PCT (with Heather's permission) because I think this is a very interesting discovery that seems to pose a challenge to PCT and I would like to see what you think about this.

> > > > > > > > > Here is section of what I wrote to Heather on this question April 12.
> > > > > > > > > 
> > > > > > > > > --------
> > > > > > > > > 
> > > > > > > > > [Here is a] quick and dirty PCT approach. I start with the intention to bat at the target, which would set a reference for a sequence that could crudely be taken as "store energy, set trigger, wait, release energy when required", or in a more general sense "Prepare, wait, execute". You call the storage "prestabilizing", but I think Powers would have called that a "dormitive principle" that just labels what happens without in any way explaining how or why. The "stabilizing" is postural control of the normal kind, the same as would happen if you pushed the cat. If you have seen a video of the "Big Dog" robot, you have seen this kind of stabilization.
> > > > > > > > > 
> > > > > > > > > The magician Harry Houdini died because he hadn't stored the energy to resist a blow to his abdomen when someone hit him before he was prepared, which he did by tensing (supplying energy to) the stomach muscles. He had offered a general challenge that nobody could hit him there hard enough to hurt him, but the hitter was supposed to do it in a formal kind of way, when he was prepared. When the fatal blow was struck, his muscles had insufficient stored energy to oppose the shock energy in the blow.
> > > > > > > > > 
> > > > > > > > > I think the actual stabilization is simply the use of some of the pre-tensioned stored energy in normal postural control against a force that would be destabilizing, but instead of the control being entirely to oppose a sensed disturbance, it is part of the output side support of the sequence controller. The "bat" is not simply sending reference values to muscles that move the paw relative to the torso, it is sending reference values to all the postural muscles in a temporal pattern that has been reorganized into the control hierarchy in the same way as a trained athlete such as a ballerina coordinates the timings and strengths of her muscle movements so that what an observer calls "the" action doesn't interfere with her balance.
> > > > > > > > > 
> > > > > > > > > Anyway, those are my first thoughts on the question, before breakfast.
> > > > > > > > > 
> > > > > > > > > -------  
> > > > > > > > > I haven't considered the problem since then, but I thought I might offer the suggestion.
> > > > > > > > > 
> > > > > > > > > The saying "Reculer pour mieux sauter" seems to be about the same phenomenon.
> > > > > > > > > 
> > > > > > > > > Martin
> > > > > > > > 
> > > > > > > > \<aruin2003.pdf\>  
> > > > > > > > \<graziano2002.pdf\>
> > > > 
> > > > --  
> > > > Heather C. Broccard-Bell, Ph.D.  
> > > > Adjunct Assistant Professor  
> > > > Department of Psychological Sciences

University of San Diego

> > > > Visiting Scholar

The role of noise / variability in complex, adaptive systems  
Nieh Honey Bee Lab  
Division of Biological Sciences; Section of Ecology, Behavior, and Evolution  
University of California San Diego

> > > > 619.757.4694
> > > 
> > > --  
> > > Heather C. Broccard-Bell, Ph.D.  
> > > Adjunct Assistant Professor  
> > > Department of Psychological Sciences

University of San Diego

> > > Visiting Scholar

The role of noise / variability in complex, adaptive systems  
Nieh Honey Bee Lab  
Division of Biological Sciences; Section of Ecology, Behavior, and Evolution  
University of California San Diego

> > > 619.757.4694
> 
> --  
> Heather C. Broccard-Bell, Ph.D.  
> Adjunct Assistant Professor  
> Department of Psychological Sciences

University of San Diego

> Visiting Scholar

The role of noise / variability in complex, adaptive systems  
Nieh Honey Bee Lab  
Division of Biological Sciences; Section of Ecology, Behavior, and Evolution  
University of California San Diego

> **···**
>
> On 5/9/19 2:49 PM, Heather Broccard-Bell (\<mailto:hebell@ucsd.edu\>hebell@ucsd.edu via csgnet Mailing List) wrote:
> 
> > On Thu, May 9, 2019 at 1:40 PM Martin Taylor \<\<mailto:csgnet@lists.illinois.edu\>csgnet@lists.illinois.edu\> wrote:
> > 
> > > On 2019/05/9 3:59 PM, Heather Broccard-Bell (\<mailto:hebell@ucsd.edu\>hebell@ucsd.edu via csgnet Mailing List) wrote:
> > > 
> > > > On Thu, May 9, 2019 at 12:58 PM Heather Broccard-Bell \<\<mailto:hebell@ucsd.edu\>hebell@ucsd.edu\> wrote:
> > > 
> > > On Thu, May 9, 2019 at 12:14 PM Martin Taylor \<\<mailto:mmt@mmtaylor.net\>mmt@mmtaylor.net\> wrote:
> > > 
> > > > > > On 2019/05/9 1:53 PM, Heather Broccard-Bell wrote:
> > > > > > 
> > > > > > > On Thu, May 9, 2019, 07:18 Warren Mansell \<\<mailto:wmansell@gmail.com\>wmansell@gmail.com\> wrote:
> > > > > > > 
> > > > > > > > On 9 May 2019, at 14:28, Heather Broccard-Bell (\<mailto:hebell@ucsd.edu\>hebell@ucsd.edu via csgnet Mailing List) \<\<mailto:csgnet@lists.illinois.edu\>csgnet@lists.illinois.edu\> wrote:
> > > > > > > > 
> > > > > > > > > On Wed, May 8, 2019, 21:16 Martin Taylor \<\<mailto:csgnet@lists.illinois.edu\>csgnet@lists.illinois.edu\> wrote:
> > 
> > 619.757.4694

---

<div class="post-metadata">

**Author:** ![wmansell](http://discourse.iapct.org/user_avatar/discourse.iapct.org/wmansell/32/36_2.png) [@wmansell](http://discourse.iapct.org/u/wmansell)\
**Post date:** [May 10, 2019, 7:52am UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/18 "2019-05-10T07:52:46Z")

</div>

> Hi folks,

> See what you make of this: [http://www.pctweb.org/FeedforwardinPCT.pdf](http://www.pctweb.org/FeedforwardinPCT.pdf)

> I need to get a full version published one day!

> Essentially the rest of psychology continue to use the word ‘prediction’ because it’s the done thing, and can’t let go of the fact that the term doesn’t best describe what they see in their data, theories and mathematical models, which often begin to converge on PCT but ultimately, don’t.

> 

> The ‘internal model’ in PCT is purely the functions and parameters that extract and control perceptual variables. Rarely should these approximate to any physical variables in the world. For example, simultaneously controlling the lateral angle, and velocity of the image of a flyball on one’s retina seems to be the best way to get to the right place to catch it. This can be computed from the physical parameters when modelling it on a computer but the brain doesn’t need to do any of this - because it’s world is perceptual, and these two neat perceptual variables dynamically update relative x and y coordinates without the brain having to do ANY computation based on the physical variables that the computer uses.

> 

> Other internal models in psychology don’t do this - they assume that the brain works like a VR machine, trying to rebuild all the physical parameters in its model, to have an simulated physics engine in the head.

> 

> The other advantage of perceptual control is that you don’t have to perceive the world accurately - in fact perceiving it in a biased way can be more efficient. Max, ccd has found, following Martin, that if in a PCT model you bias the perception of target position by its current velocity so it looks further along its path than it really is, then the model is a more accurate match with human tracking. This looks like anticipation from the outside, but it’s actually controlling for a biased perception that doesn’t currently exist in the world, but will do in a fraction of a second, but the brain doesn’t need to know this.

> 

> Please reply as I do want to check Rick, Martin, Bill, Heather, etc, agree?

> 

> Cheers,

> 

> Warren

> 

> 

> 

> >

> **···**
>
> On 5/9/19 2:49 PM, Heather  
> Broccard-Bell ( via csgnet Mailing List) wrote:
> 
> hebell@ucsd.edu
> 
> > ```
> > I agree, nobody is actively making a prediction,
> > 
> > ```
> > 
> > but the system is tuned to perform better in the world as it as  
> > previously experienced it (as stated), because mostly this works  
> > out – because often the world is kind of consistent. What  
> > makes a prediction different, and what then does it mean to make  
> > a prediction? Does a prediction have to be a fully-formed set  
> > of anticipated data? I think I am not understanding what makes  
> > “prediction” different from “bias based on past experience”.
> 
> ```
> I suggest that "bias based on past
> 
> ```
> 
> experience" is the basis for all prediction with respect to  
> control system operation. The term prediction also encompasses  
> things like “the world is going to end in 12 years” which I  
> think it is reasonable to assume is not experience based.
> 
> bill
> 
> > ```
> > On Thu, May 9, 2019 at 1:40 PM
> > 
> > ```
> > 
> > Martin Taylor \<csgnet@lists.illinois.edu \>  
> > wrote:
> 
> > > [Martin Taylor 2019.05.09.16.13]
> > > 
> > > ```
> > > On
> > > 
> > > ```
> > > 
> > > 2019/05/9 3:59 PM, Heather Broccard-Bell (hebell@ucsd.edu via csgnet  
> > > Mailing List) wrote:
> 
> > > > ```
> > > > Sorry, that was meant to go to everyone,
> > > > 
> > > > ```
> > > > 
> > > > not just Martin 🙂
> 
> > > > ```
> > > > On Thu, May 9, 2019
> > > > 
> > > > ```
> > > > 
> > > > at 12:58 PM Heather Broccard-Bell \<hebell@ucsd.edu \>  
> > > > wrote:
> 
> > > > > ```
> > > > > All right, so what then is the
> > > > > 
> > > > > ```
> > > > > 
> > > > > difference between operating on a reference signal  
> > > > > from an internal model, and making a prediction?
> 
> > > ```
> > > If you call the intended result of an action (bringing a
> > > 
> > > ```
> > > 
> > > perception toward its reference value) a prediction, I would  
> > > say that’s a strange use of “prediction”. better  
> > > understanding of what is going on. If I decide to go out and  
> > > do go out, have I predicted that I will go out? The Friston  
> > > “Free Energy” people say exactly that, probably for the  
> > > reasons you suggest below. I would call it at best a  
> > > self-fulfilling prediction, one that comes to pass because  
> > > of the actions of the one who predicts and wouldn’t come to  
> > > pass in the absence of those actions.
> > > 
> > > > > ```
> > > > > Does that not amount to the same
> > > > > 
> > > > > ```
> > > > > 
> > > > > thing? After all, the parameters of the internal  
> > > > > model are set through experience (or evolution –  
> > > > > which is some kind of sort of larger  
> > > > > “experience”). So then the system can be biased  
> > > > > in a way that allows it to function better than  
> > > > > ones that aren’t biased that way in a given  
> > > > > environment.
> 
> > > ```
> > > I could be happy with saying that there is a form of
> > > 
> > > ```
> > > 
> > > prediction here, which is a prediction that the Real Reality  
> > > world will continue to act much as it has been acting for a  
> > > reasonably long time. It’s not a prediction that when the  
> > > cat wants to bat at something it will do what is necessary  
> > > to bat at the thing without falling over. But who is  
> > > predicting? Nobody. Both evolution and reorganization work  
> > > with past data, not predicted future data. The “prediction”  
> > > is simply the working of Natural Law, whether we know the  
> > > law or not.
> > > 
> > > ```
> > > Martin
> > > 
> > > On Thu, May 9, 2019 at 12:14 PM Martin Taylor <mmt@mmtaylor.net> wrote:
> > > 
> > > ```
> > > 
> > > > > > ```
> > > > > > [Martin Taylor
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > 2019.05.09.14.35]
> > > > > > 
> > > > > > ```
> > > > > > On
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > 2019/05/9 1:53 PM, Heather Broccard-Bell  
> > > > > > wrote:
> 
> > > > > > > ```
> > > > > > > I'm still not sure I
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > satisfactorily answered my own original  
> > > > > > > question, though. And also, if we can  
> > > > > > > compensate for a predicted disturbance  
> > > > > > > (even if we can update our compensation  
> > > > > > > when the compensation is perturbed), the  
> > > > > > > original reference signal is presumably  
> > > > > > > coming from some kind of internal model,  
> > > > > > > no? Is this cool? I thought we were  
> > > > > > > anti-internal model (except for super  
> > > > > > > sophisticated human cognition where we do  
> > > > > > > clearly imagine things)? This suggests  
> > > > > > > cats have one, no?
> 
> > > > > > ```
> > > > > > I guess your question is about what the
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > pre-stored energy in the cats muscles is for,  
> > > > > > and whether it implies prediction of an  
> > > > > > external disturbance. I don’t think it does.  
> > > > > > Remember that reference values change, and  
> > > > > > that reorganization changes parameters and  
> > > > > > level-to-level interconnection parameters.  
> > > > > > Maybe the first time the cat ever tried to bat  
> > > > > > at something it didn’t hit it properly, and  
> > > > > > maybe it stumbled or fell after the attempt.  
> > > > > > Nothing of that happened before the cat tried  
> > > > > > to compensate for a disturbance from outside,  
> > > > > > so there’s no prediction involved. No  
> > > > > > subsequent unpredicted disturbance is involved  
> > > > > > in your question.
> > > > > > 
> > > > > > ```
> > > > > > Everything else is internally generated as
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > changing reference values feed down the levels  
> > > > > > of control all the way to the individual  
> > > > > > muscle tension control loops. The feedback  
> > > > > > effects of the actions generated by the  
> > > > > > control units whose reference levels were  
> > > > > > changed are fairly consistent over many  
> > > > > > attempts at batting at locally moving things  
> > > > > > (as an observer sees it), so reorganization  
> > > > > > has the opportunity to build the proper  
> > > > > > coordinations and sequences of muscle  
> > > > > > tensions.
> > > > > > 
> > > > > > ```
> > > > > > Yes, there's an internal model. It's in the
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > reorganized connections and parameter settings  
> > > > > > for the control loops used to do the batting,  
> > > > > > and part of that is pre-tensioning the muscles  
> > > > > > both to perform the bat and to reduce the  
> > > > > > sudden effect of the action until fast normal  
> > > > > > low-level control loops correct any remaining  
> > > > > > perceptual errors. I bet you do the same if  
> > > > > > you pick up a pile of dishes to put them on a  
> > > > > > shelf. If you started out with slack muscles,  
> > > > > > you might fall when you picked them up, and  
> > > > > > when you released them onto the shelf you  
> > > > > > might fall in the other direction if all the  
> > > > > > tension was devoted to holding up the plates,  
> > > > > > rather than to compensate for the change in  
> > > > > > balance, which you have encountered every time  
> > > > > > you picked up or released a weight since you  
> > > > > > were old enough to try.
> > > > > > 
> > > > > > ```
> > > > > > It might be evolution, not primarily
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > reorganization in the individual cat, though,  
> > > > > > because cats are notoriously good at keeping  
> > > > > > their attitude with respect to gravity,  
> > > > > > landing with feet toward the ground if falling  
> > > > > > from a height, and performing remarkable rapid  
> > > > > > body contortions while remaining stable.
> > > > > > 
> > > > > > ```
> > > > > > Martin
> > > > > > 
> > > > > > ```
> > > > > > 
> > > > > > >
> 
> > > > > > > ```
> > > > > > > On
> > > > > > > 
> > > > > > > ```
> > > > > > > 
> > > > > > > Thu, May 9, 2019, 07:18 Warren  
> > > > > > > Mansell \<[wmansell@gmail.com](mailto:wmansell@gmail.com) \>  
> > > > > > > wrote:
> 
> > > > > > > > ```
> > > > > > > > Hurray, PCT wins!
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > But do any of the readers of  
> > > > > > > > these papers realise?
> 
> > > > > > > >
> 
> > > > > > > > ```
> > > > > > > > On 9 May 2019, at 14:28, Heather
> > > > > > > > 
> > > > > > > > ```
> > > > > > > > 
> > > > > > > > Broccard-Bell (hebell@ucsd.edu  
> > > > > > > > via csgnet Mailing List) \<csgnet@lists.illinois.edu \>  
> > > > > > > > wrote:
> 
> > > > > > > > >
> 
> > > > > > > > > ```
> > > > > > > > > I
> > > > > > > > > 
> > > > > > > > > ```
> > > > > > > > > 
> > > > > > > > > suspect that the  
> > > > > > > > > attached (Aruin, 2003)  
> > > > > > > > > paper goes some way  
> > > > > > > > > toward reconciling the  
> > > > > > > > > “invariant,  
> > > > > > > > > pre-programmed”  
> > > > > > > > > feedforward  
> > > > > > > > > conceptualization with  
> > > > > > > > > the actual phenomenon:  
> > > > > > > > > namely, it’s not  
> > > > > > > > > really invariant (or,  
> > > > > > > > > well, it’s not  
> > > > > > > > > invariant in that  
> > > > > > > > > there is a  
> > > > > > > > > pre-programmed set of  
> > > > > > > > > muscles activated in a  
> > > > > > > > > pre-programmed way).  
> > > > > > > > > So, I suspect that  
> > > > > > > > > some of the problem in  
> > > > > > > > > the “mainstream” is  
> > > > > > > > > semantic.
> 
> > > > > > > > > ```
> > > > > > > > > Anyway,
> > > > > > > > > 
> > > > > > > > > ```
> > > > > > > > > 
> > > > > > > > > long (~500 ms)  
> > > > > > > > > stimulation of motor  
> > > > > > > > > cortex has already  
> > > > > > > > > demonstrated that  
> > > > > > > > > “motor output” seems  
> > > > > > > > > to be about goals,  
> > > > > > > > > and not specific,  
> > > > > > > > > muscle-by-muscle  
> > > > > > > > > motor programs (see  
> > > > > > > > > Graziano, 2002;  
> > > > > > > > > attached), and  
> > > > > > > > > really the only way  
> > > > > > > > > you could get that  
> > > > > > > > > to work is  
> > > > > > > > > hierarchical control  
> > > > > > > > > with continuous  
> > > > > > > > > feedback…
> 
> > > > > > > > > ```
> > > > > > > > > On
> > > > > > > > > 
> > > > > > > > > ```
> > > > > > > > > 
> > > > > > > > > Wed, May 8, 2019,  
> > > > > > > > > 21:16 Martin Taylor  
> > > > > > > > > \<csgnet@lists.illinois.edu \>  
> > > > > > > > > wrote:
> 
> > > > > > > > > > ```
> > > > > > > > > > [Martin Taylor
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > 2019.05.09.00.09]
> > > > > > > > > > 
> > > > > > > > > > > ```
> > > > > > > > > > > [Rick
> > > > > > > > > > > 
> > > > > > > > > > > ```
> > > > > > > > > > > 
> > > > > > > > > > > Marken  
> > > > > > > > > > > 2019-05-08\_17:57:30]
> 
> > > > > > > > > > >
> 
> > > > > > > > > > > ```
> > > > > > > > > > > RM: Some
> > > > > > > > > > > 
> > > > > > > > > > > ```
> > > > > > > > > > > 
> > > > > > > > > > > time ago  
> > > > > > > > > > > Heather  
> > > > > > > > > > > Broccard-Bell  
> > > > > > > > > > > asked me what  
> > > > > > > > > > > the PCT  
> > > > > > > > > > > explanation  
> > > > > > > > > > > might be of a  
> > > > > > > > > > > behavior that  
> > > > > > > > > > > looks like a  
> > > > > > > > > > > pretty robust  
> > > > > > > > > > > example of  
> > > > > > > > > > > anticipatory  
> > > > > > > > > > > (or  
> > > > > > > > > > > feedforward)  
> > > > > > > > > > > control.  
> > > > > > > > > > > Here’s how  
> > > > > > > > > > > Heather  
> > > > > > > > > > > described it  
> > > > > > > > > > > to me:
> 
> > > > > > > > > > >
> 
> > > > > > > > > > > > ```
> > > > > > > > > > > > HB-B:
> > > > > > > > > > > > 
> > > > > > > > > > > > ```
> > > > > > > > > > > > 
> > > > > > > > > > > > I was reading  
> > > > > > > > > > > > about this  
> > > > > > > > > > > > finding (and  
> > > > > > > > > > > > perhaps you  
> > > > > > > > > > > > are already  
> > > > > > > > > > > > familiar)  
> > > > > > > > > > > > that, if if  
> > > > > > > > > > > > you measure  
> > > > > > > > > > > > muscle  
> > > > > > > > > > > > activation  
> > > > > > > > > > > > during  
> > > > > > > > > > > > behavior, you  
> > > > > > > > > > > > often see  
> > > > > > > > > > > > compensatory  
> > > > > > > > > > > > activation of  
> > > > > > > > > > > > the axial  
> > > > > > > > > > > > musculature  
> > > > > > > > > > > > well before  
> > > > > > > > > > > > you get  
> > > > > > > > > > > > activation in  
> > > > > > > > > > > > the muscles  
> > > > > > > > > > > > that direct  
> > > > > > > > > > > > the part of  
> > > > > > > > > > > > the body that  
> > > > > > > > > > > > does the thing  
> > > > > > > > > > > > you’re focused  
> > > > > > > > > > > > on. For  
> > > > > > > > > > > > example, they  
> > > > > > > > > > > > trained cats  
> > > > > > > > > > > > to bat at a  
> > > > > > > > > > > > target with  
> > > > > > > > > > > > their  
> > > > > > > > > > > > forepaw. \*\* Well  
> > > > > > > > > > > > before the  
> > > > > > > > > > > > limb/forepaw  
> > > > > > > > > > > > muscles are  
> > > > > > > > > > > > active, there  
> > > > > > > > > > > > is activation  
> > > > > > > > > > > > in the trunk  
> > > > > > > > > > > > musculature,  
> > > > > > > > > > > > seemingly  
> > > > > > > > > > > > anticipating  
> > > > > > > > > > > > the requisite  
> > > > > > > > > > > > compensatory  
> > > > > > > > > > > > stabilization  
> > > > > > > > > > > > that will  
> > > > > > > > > > > > become  
> > > > > > > > > > > > necessary when  
> > > > > > > > > > > > the forepaw is  
> > > > > > > > > > > > lifted. \*\* I  
> > > > > > > > > > > > am wondering  
> > > > > > > > > > > > what a PCT  
> > > > > > > > > > > > perspective  
> > > > > > > > > > > > might be on  
> > > > > > > > > > > > that? What is  
> > > > > > > > > > > > the relevant  
> > > > > > > > > > > > controlled  
> > > > > > > > > > > > variable,  
> > > > > > > > > > > > since the  
> > > > > > > > > > > > thing that  
> > > > > > > > > > > > actually  
> > > > > > > > > > > > changes  
> > > > > > > > > > > > sensory input  
> > > > > > > > > > > > that should  
> > > > > > > > > > > > activate  
> > > > > > > > > > > > control  
> > > > > > > > > > > > architecture  
> > > > > > > > > > > > hasn’t yet  
> > > > > > > > > > > > happened? Am  
> > > > > > > > > > > > I missing  
> > > > > > > > > > > > something? It  
> > > > > > > > > > > > appears to be  
> > > > > > > > > > > > a rather  
> > > > > > > > > > > > robust  
> > > > > > > > > > > > finding.[emphasis  
> > > > > > > > > > > > mine–RM]
> 
> > > > > > > > > > > …
> 
> > > > > > > > > > > ```
> > > > > > > > > > > RM:
> > > > > > > > > > > 
> > > > > > > > > > > ```
> > > > > > > > > > > 
> > > > > > > > > > > I am posting  
> > > > > > > > > > > this to you  
> > > > > > > > > > > experts on PCT  
> > > > > > > > > > > (with  
> > > > > > > > > > > Heather’s  
> > > > > > > > > > > permission)  
> > > > > > > > > > > because I  
> > > > > > > > > > > think this is  
> > > > > > > > > > > a very  
> > > > > > > > > > > interesting  
> > > > > > > > > > > discovery that  
> > > > > > > > > > > seems to pose  
> > > > > > > > > > > a challenge to  
> > > > > > > > > > > PCT and I  
> > > > > > > > > > > would like to  
> > > > > > > > > > > see what you  
> > > > > > > > > > > think about  
> > > > > > > > > > > this.
> 
> > > > > > > > > > ```
> > > > > > > > > > Here is section
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > of what I wrote to  
> > > > > > > > > > Heather on this  
> > > > > > > > > > question April 12.
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > --------
> > > > > > > > > > 
> > > > > > > > > > [Here is a] quick
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > and dirty PCT  
> > > > > > > > > > approach. I start  
> > > > > > > > > > with the intention  
> > > > > > > > > > to bat at the  
> > > > > > > > > > target, which  
> > > > > > > > > > would set a  
> > > > > > > > > > reference for a  
> > > > > > > > > > sequence that  
> > > > > > > > > > could crudely be  
> > > > > > > > > > taken as “store  
> > > > > > > > > > energy, set  
> > > > > > > > > > trigger, wait,  
> > > > > > > > > > release energy  
> > > > > > > > > > when required”, or  
> > > > > > > > > > in a more general  
> > > > > > > > > > sense “Prepare,  
> > > > > > > > > > wait, execute”.  
> > > > > > > > > > You call the  
> > > > > > > > > > storage  
> > > > > > > > > > “prestabilizing”,  
> > > > > > > > > > but I think Powers  
> > > > > > > > > > would have called  
> > > > > > > > > > that a “dormitive  
> > > > > > > > > > principle” that  
> > > > > > > > > > just labels what  
> > > > > > > > > > happens without in  
> > > > > > > > > > any way explaining  
> > > > > > > > > > how or why. The  
> > > > > > > > > > “stabilizing” is  
> > > > > > > > > > postural control  
> > > > > > > > > > of the normal  
> > > > > > > > > > kind, the same as  
> > > > > > > > > > would happen if  
> > > > > > > > > > you pushed the  
> > > > > > > > > > cat. If you have  
> > > > > > > > > > seen a video of  
> > > > > > > > > > the “Big Dog”  
> > > > > > > > > > robot, you have  
> > > > > > > > > > seen this kind of  
> > > > > > > > > > stabilization.
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > The magician Harry
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > Houdini died  
> > > > > > > > > > because he hadn’t  
> > > > > > > > > > stored the energy  
> > > > > > > > > > to resist a blow  
> > > > > > > > > > to his abdomen  
> > > > > > > > > > when someone hit  
> > > > > > > > > > him before he was  
> > > > > > > > > > prepared, which he  
> > > > > > > > > > did by tensing  
> > > > > > > > > > (supplying energy  
> > > > > > > > > > to) the stomach  
> > > > > > > > > > muscles. He had  
> > > > > > > > > > offered a general  
> > > > > > > > > > challenge that  
> > > > > > > > > > nobody could hit  
> > > > > > > > > > him there hard  
> > > > > > > > > > enough to hurt  
> > > > > > > > > > him, but the  
> > > > > > > > > > hitter was  
> > > > > > > > > > supposed to do it  
> > > > > > > > > > in a formal kind  
> > > > > > > > > > of way, when he  
> > > > > > > > > > was prepared. When  
> > > > > > > > > > the fatal blow was  
> > > > > > > > > > struck, his  
> > > > > > > > > > muscles had  
> > > > > > > > > > insufficient  
> > > > > > > > > > stored energy to  
> > > > > > > > > > oppose the shock  
> > > > > > > > > > energy in the  
> > > > > > > > > > blow.
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > I think the actual
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > stabilization is  
> > > > > > > > > > simply the use of  
> > > > > > > > > > some of the  
> > > > > > > > > > pre-tensioned  
> > > > > > > > > > stored energy in  
> > > > > > > > > > normal postural  
> > > > > > > > > > control against a  
> > > > > > > > > > force that would  
> > > > > > > > > > be destabilizing,  
> > > > > > > > > > but instead of the  
> > > > > > > > > > control being  
> > > > > > > > > > entirely to oppose  
> > > > > > > > > > a sensed  
> > > > > > > > > > disturbance, it is  
> > > > > > > > > > part of the output  
> > > > > > > > > > side support of  
> > > > > > > > > > the sequence  
> > > > > > > > > > controller. The  
> > > > > > > > > > “bat” is not  
> > > > > > > > > > simply sending  
> > > > > > > > > > reference values  
> > > > > > > > > > to muscles that  
> > > > > > > > > > move the paw  
> > > > > > > > > > relative to the  
> > > > > > > > > > torso, it is  
> > > > > > > > > > sending reference  
> > > > > > > > > > values to all the  
> > > > > > > > > > postural muscles  
> > > > > > > > > > in a temporal  
> > > > > > > > > > pattern that has  
> > > > > > > > > > been reorganized  
> > > > > > > > > > into the control  
> > > > > > > > > > hierarchy in the  
> > > > > > > > > > same way as a  
> > > > > > > > > > trained athlete  
> > > > > > > > > > such as a  
> > > > > > > > > > ballerina  
> > > > > > > > > > coordinates the  
> > > > > > > > > > timings and  
> > > > > > > > > > strengths of her  
> > > > > > > > > > muscle movements  
> > > > > > > > > > so that what an  
> > > > > > > > > > observer calls  
> > > > > > > > > > “the” action  
> > > > > > > > > > doesn’t interfere  
> > > > > > > > > > with her balance.
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > Anyway, those are
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > my first thoughts  
> > > > > > > > > > on the question,  
> > > > > > > > > > before breakfast.
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > -------
> > > > > > > > > > 
> > > > > > > > > > I haven't
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > considered the  
> > > > > > > > > > problem since  
> > > > > > > > > > then, but I  
> > > > > > > > > > thought I might  
> > > > > > > > > > offer the  
> > > > > > > > > > suggestion.
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > The saying
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > 
> > > > > > > > > > “Reculer pour  
> > > > > > > > > > mieux sauter”  
> > > > > > > > > > seems to be about  
> > > > > > > > > > the same  
> > > > > > > > > > phenomenon.
> > > > > > > > > > 
> > > > > > > > > > ```
> > > > > > > > > > Martin
> > > > > > > > > > 
> > > > > > > > > > ```
> 
> > > > > > > > > \<aruin2003.pdf\>
> 
> > > > > > > > > \<graziano2002.pdf\>
> 
> > > > > >
> 
> > > > >
> 
> > > > > –  
> > > > > Heather  
> > > > > C. Broccard-Bell,  
> > > > > Ph.D.
> 
> > > > >
> 
> > > > > Adjunct Assistant Professor
> 
> > > > > ```
> > > > > Department
> > > > > 
> > > > > ```
> > > > > 
> > > > > of  
> > > > > Psychological  
> > > > > Sciences
> 
> > > > > ```
> > > > > University
> > > > > 
> > > > > ```
> > > > > 
> > > > > of San Diego
> 
> > > > >
> 
> > > > > ```
> > > > > Visiting
> > > > > 
> > > > > ```
> > > > > 
> > > > > Scholar
> 
> > > > > ```
> > > > > The
> > > > > 
> > > > > ```
> > > > > 
> > > > > role of noise /  
> > > > > variability in  
> > > > > complex,  
> > > > > adaptive systems
> 
> > > > > ```
> > > > > Nieh
> > > > > 
> > > > > ```
> > > > > 
> > > > > Honey Bee Lab
> 
> > > > > ```
> > > > > Division
> > > > > 
> > > > > ```
> > > > > 
> > > > > of Biological  
> > > > > Sciences;  
> > > > > Section of  
> > > > > Ecology,  
> > > > > Behavior, and  
> > > > > Evolution
> 
> > > > > ```
> > > > > University
> > > > > 
> > > > > ```
> > > > > 
> > > > > of California  
> > > > > San Diego
> 
> > > > > ```
> > > > > 619.757.4694
> > > > > 
> > > > > ```
> 
> > > >
> 
> > > > –  
> > > > Heather  
> > > > C. Broccard-Bell,  
> > > > Ph.D.
> 
> > > >
> 
> > > > ```
> > > > Adjunct
> > > > 
> > > > ```
> > > > 
> > > > Assistant  
> > > > Professor
> 
> > > > ```
> > > > Department
> > > > 
> > > > ```
> > > > 
> > > > of Psychological  
> > > > Sciences
> 
> > > > ```
> > > > University
> > > > 
> > > > ```
> > > > 
> > > > of San Diego
> 
> > > >
> 
> > > > ```
> > > > Visiting
> > > > 
> > > > ```
> > > > 
> > > > Scholar
> 
> > > > ```
> > > > The
> > > > 
> > > > ```
> > > > 
> > > > role of noise /  
> > > > variability in  
> > > > complex, adaptive  
> > > > systems
> 
> > > > ```
> > > > Nieh
> > > > 
> > > > ```
> > > > 
> > > > Honey Bee Lab
> 
> > > > ```
> > > > Division
> > > > 
> > > > ```
> > > > 
> > > > of Biological  
> > > > Sciences; Section of  
> > > > Ecology, Behavior,  
> > > > and Evolution
> 
> > > > ```
> > > > University
> > > > 
> > > > ```
> > > > 
> > > > of California San  
> > > > Diego
> 
> > > > ```
> > > > 619.757.4694
> > > > 
> > > > ```
> 
> > >
> 
> > 
> 
> > –  
> > Heather C.  
> > Broccard-Bell, Ph.D.
> 
> > 
> 
> > ```
> > Adjunct
> > 
> > ```
> > 
> > Assistant Professor
> 
> > ```
> > Department
> > 
> > ```
> > 
> > of Psychological Sciences
> 
> > ```
> > University
> > 
> > ```
> > 
> > of San Diego
> 
> > 
> 
> > ```
> > Visiting
> > 
> > ```
> > 
> > Scholar
> 
> > ```
> > The role of
> > 
> > ```
> > 
> > noise / variability in  
> > complex, adaptive systems
> 
> > ```
> > Nieh Honey Bee
> > 
> > ```
> > 
> > Lab
> 
> > ```
> > Division of
> > 
> > ```
> > 
> > Biological Sciences; Section  
> > of Ecology, Behavior, and  
> > Evolution
> 
> > ```
> > University of
> > 
> > ```
> > 
> > California San Diego
> 
> > ```
> > 619.757.4694
> > 
> > ```

---

<div class="post-metadata">

**Author:** ![MartinT](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/m/ee7513/32.png) [@MartinT](http://discourse.iapct.org/u/MartinT)\
**Post date:** [May 10, 2019, 2:32pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/19 "2019-05-10T14:32:23Z")

</div>

[Martin Taylor 2019.05.10.10.08]

```
Well put. The first paragraph more or less offers the basis for what

```

I have been trying to get across, less skilfully, in the RREV-CEV  
discussion. The RREV is the fact, the CEV is the model. The second paragraph follows the Friston “Free Energy” way of  
thinking, which is – I claim – largely embodied in PCT, but which  
is somewhat misleading in its wording and in the thinking that leads  
to the labels given to its elements. In that context, every action  
is based upon a future need for any part of the  
hierarchy that has been reorganized. The PCT wording would say that  
whatever in the hierarchy is used to reduce the difference between  
the perception and its reference value is an available means to  
control the perceptual variable. You might say that the need was by evolution or  
reorganization if you wanted to be teleological and say that some  
agent in the past knew that the cat would at some future time want  
to bat at a moving object. I would prefer to say that the useful  
part of the hierarchy was in place to be used for “batting” because  
of the survival and incremental modification of elements that had  
been useful in the past for that and other purposes.  
It certainly is possible to construct things because of an  
anticipated future need. Teachers of mathematics to children are  
trying to do just that. The teacher or whoever prescribed the  
curriculum presumably is controlling a perception that at some  
future time most children will be able to control some perceptions  
better if they have available the tools of mathematics. I would call  
that a prediction, but even that might be open to argument.  
Martin

> **···**
>
> On 2019/05/9 6:02 PM, Bill Leach  
> ( via csgnet Mailing List) wrote:
> 
> [wrleach@cableone.net](mailto:wrleach@cableone.net)
> 
> > ```
> > ...Indeed, even Martin's example of sequencing involves a model in
> > 
> > ```
> > 
> > that the sequence **is** a model. In a specific subject that  
> > model was either constructed or inherited but at some point, maybe  
> > eons ago it was constructed. Some form or reorganization was  
> > involved in the construction to correct for uncontrolled or poorly  
> > controlled error.  
> > “Pre-action tensioning” is a fine label for the sequence step  
> > but keep in mind that the whole sequence is based upon _anticipating_  
> > the need to run the sequence to ensure satisfactory control of  
> > perception including an expected future perception.
> 
> > 
> 
> _anticipating_  
> _anticipated_

---

<div class="post-metadata">

**Author:** ![\_Erling\_Jorgensen](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/_/58956e/32.png) [@\_Erling\_Jorgensen](http://discourse.iapct.org/u/_Erling_Jorgensen)\
**Post date:** [May 10, 2019, 5:38pm UTC](http://discourse.iapct.org/t/anticipatory-postural-control/1164/20 "2019-05-10T17:38:25Z")

</div>

[From Erling Jorgensen (2019.05.10 1243 EDT)]

> Rick Marken 2019-05-08\_17:57:30

> > 2019/05/9 6:02 PM, Bill Leach…

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> > > Martin Taylor 2019.05.10.10.08

> > BL: “Pre-action tensioning” is a fine label for the sequence step but keep in mind that the whole sequence is based upon _anticipating_ the need to run the sequence to ensure satisfactory control of perception including an expected future perception.

EJ: I believe this is one of the questions at issue. Does a PCT control system, using negative feedback in present time, controlling for a sequence perception or some other type of complicated body configuration, specifically need “anticipation” to carry out its control?

EJ: I also have a concern about the last three words of the above quote. While technically a PCT goal (i.e., reference standard) could be called “an expected future perception,” I believe that pre-decides the question, by leaving open the implication that PCT control has to operate by means of … [fill in the blank]: some call it “anticipation,” some call it “prediction,” some call if “feedforward mechanisms.” There are ways for a PCT hierarchy to handle such processes, but I don’t think we say they are necessary for PCT control.

> > > MT: You might say that the need was _anticipated_ by evolution or reorganization if you wanted to be teleological and say that some agent in the past knew that the cat would at some future time want to bat at a moving object. I would prefer to say that the useful part of the hierarchy was in place to be used for “batting” because of the survival and incremental modification of elements that had been useful in the past for that and other purposes.

EJ: I thought Heather’s original raising of anticipation was in a different context. Here’s the relevant passage, quoted by:

> Rick Marken 2019-05-08\_17:57:30 –

> HB-B: … \*\*Well before the limb/forepaw muscles are active, there is activation in the trunk musculature, seemingly anticipating the requisite compensatory stabilization that will become necessary when the forepaw is lifted. \*\*

EJ: This is the “behavior that looks like a pretty robust example of anticipatory (or feedforward) control.” To my mind, “anticipating” here is not about the processes of either evolution or reorganization in constructing the elementary control systems that may be involved. It seems rather to be about producing specific values within those control systems during a specific situation, values that show themselves as changes of perception, reference, or output.

EJ: While I have only skimmed the research papers that both Rick & Heather attached, the ‘pre-action tensioning’ (as I’ll continue to call the phenomenon) seems at odds with a prediction of the PCT model. Rick expressed the issue well:

> RM: This finding certainly looks like it is inconsistent with the predictions of PCT since it looks like the cat is generating an output (activation of the trunk musculature) open loop in anticipation of a future disturbance (the change in orientation of the body when the forepaw is lifted, a change in orientation that would cause the cat to lose its balance if the trunk were not in the proper position).

EJ: I don’t want PCT to prematurely surrender the field, by saying, yes of course this has to be feedforward. Does it?? Henry Yin has published some pretty strong arguments that “posture control” is a robust negative feedback control process, readily compatible with PCT as it stands. How much of this phenomenon can the current model of PCT handle?

All the best,

Erling

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